diff --git a/internal/dqs/category/abbreviations.go b/internal/dqs/category/abbreviations.go
new file mode 100644
index 0000000..8c743bd
--- /dev/null
+++ b/internal/dqs/category/abbreviations.go
@@ -0,0 +1,22 @@
+package category
+
+var Abbreviations = map[string]string{
+	// High Quality
+	"d":    Dairy.Name,
+	"f":    Fruit.Name,
+	"hqb":  HQBeverages.Name,
+	"hqpf": HQProcessedFoods.Name,
+	"lpp":  LegumesPlantProteins.Name,
+	"nsh":  NutsSeedsHealthyOils.Name,
+	"ums":  UnprocessedMeatSeafood.Name,
+	"v":    Vegetables.Name,
+	"wg":   WholeGrains.Name,
+
+	// Low Quality
+	"ff":  FriedFoods.Name,
+	"lqb": LQBeverages.Name,
+	"o":   Other.Name,
+	"p":   ProcessedMeat.Name,
+	"rg":  RefinedGrains.Name,
+	"s":   Sweets.Name,
+}
diff --git a/internal/dqs/category/category.go b/internal/dqs/category/category.go
new file mode 100644
index 0000000..dba0e10
--- /dev/null
+++ b/internal/dqs/category/category.go
@@ -0,0 +1,130 @@
+package category
+
+import (
+	"fmt"
+	"strings"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/portion"
+	"code.chimeric.al/dwrz/dqs/pkg/color"
+)
+
+// Category represents a food category and its six daily portion slots.
+// Portions are ordered from first consumed to last consumed; point values
+// decrease as more portions are eaten.
+type Category struct {
+	Name        string            `json:"name"`
+	Portions    []portion.Portion `json:"portions"`
+	HighQuality bool              `json:"highQuality"`
+}
+
+// Add fills portion slots from left to right.
+// Half-filled slots are completed before empty slots are used.
+// It returns an error if q exceeds the remaining capacity of the category.
+func (c *Category) Add(q float64) error {
+	for i := range c.Portions {
+		p := &c.Portions[i]
+		// Done if there's less than a half-portion left.
+		if q < 0.5 {
+			break
+		}
+
+		switch p.Amount {
+		case portion.Full:
+			continue
+		case portion.Half:
+			p.Amount = portion.Full
+			q -= 0.5
+		case portion.None:
+			if q >= 1.0 {
+				p.Amount = portion.Full
+				q -= 1.0
+			} else if q >= 0.5 {
+				p.Amount = portion.Half
+				q -= 0.5
+			}
+		}
+	}
+
+	// Check if we were able to add all the portions.
+	if q >= 0.5 {
+		return fmt.Errorf("too many portions of %s", c.Name)
+	}
+
+	return nil
+}
+
+// Score returns the sum of points across all portion slots in the category.
+func (c *Category) Score() (total float64) {
+	for _, p := range c.Portions {
+		total += p.Score()
+	}
+
+	return total
+}
+
+// FormatPrint formats the category as a single table row with ANSI colors.
+// Full portions color the cell background; half portions color the text.
+func (c *Category) FormatPrint() string {
+	var str strings.Builder
+	fmt.Fprintf(&str, "│%-26s│", c.Name)
+
+	for _, p := range c.Portions {
+		var cellColor color.Color
+
+		switch {
+		case p.Points > 0 && p.Amount == portion.Full:
+			cellColor = color.BackgroundBrightGreen
+		case p.Points > 0 && p.Amount == portion.Half:
+			cellColor = color.BrightGreen
+		case p.Points == 0 && p.Amount == portion.Full:
+			cellColor = color.BackgroundBrightYellow
+		case p.Points == 0 && p.Amount == portion.Half:
+			cellColor = color.BrightYellow
+		case p.Points < 0 && p.Amount == portion.Full:
+			cellColor = color.BackgroundBrightRed
+		case p.Points < 0 && p.Amount == portion.Half:
+			cellColor = color.BrightRed
+		}
+
+		fmt.Fprintf(
+			&str, "%s%+d%s│", cellColor, p.Points, color.Reset,
+		)
+	}
+
+	return str.String()
+}
+
+// Remove clears portion slots from right to left, reversing the order of Add.
+// It returns an error if q exceeds the consumed portions in the category.
+func (c *Category) Remove(q float64) error {
+	for i := len(c.Portions) - 1; i >= 0; i-- {
+		p := &c.Portions[i]
+		// Done if there's less than a half-portion left.
+		if q < 0.5 {
+			break
+		}
+
+		switch p.Amount {
+		case portion.None:
+			continue
+		case portion.Half:
+			p.Amount = portion.None
+			q -= 0.5
+		case portion.Full:
+			if q >= 1.0 {
+				p.Amount = portion.None
+				q -= 1.0
+			} else if q >= 0.5 {
+				p.Amount = portion.Half
+				q -= 0.5
+			}
+		}
+	}
+
+	// Check if we were able to remove all the portions.
+	if q >= 0.5 {
+		return fmt.Errorf("too many portions of %s", c.Name)
+	}
+
+	return nil
+}
diff --git a/internal/dqs/category/category_test.go b/internal/dqs/category/category_test.go
new file mode 100644
index 0000000..0eb48a9
--- /dev/null
+++ b/internal/dqs/category/category_test.go
@@ -0,0 +1,60 @@
+package category
+
+import (
+	"testing"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/portion"
+)
+
+func testDairy() Category {
+	var c = Dairy
+	c.Portions = make([]portion.Portion, len(Dairy.Portions))
+	copy(c.Portions, Dairy.Portions)
+	return c
+}
+
+func TestAddRemoveScore(t *testing.T) {
+	c := testDairy()
+
+	// Dairy points: +2, +1, +1, 0, -1, -2.
+	if err := c.Add(1.5); err != nil {
+		t.Fatalf("Add(1.5) error = %v", err)
+	}
+	if got := c.Score(); got != 2.5 {
+		t.Errorf("Score() = %v, want 2.5", got)
+	}
+
+	// Add 0.5 to complete the second slot (+1) and 1.0 to fill the third (+1).
+	if err := c.Add(1.5); err != nil {
+		t.Fatalf("Add(1.5) error = %v", err)
+	}
+	if got := c.Score(); got != 4.0 {
+		t.Errorf("Score() = %v, want 4.0", got)
+	}
+
+	// Fill remaining 3 slots (0, -1, -2).
+	if err := c.Add(3.0); err != nil {
+		t.Fatalf("Add(3.0) error = %v", err)
+	}
+	if got := c.Score(); got != 1.0 {
+		t.Errorf("Score() = %v, want 1.0", got)
+	}
+
+	// Adding even 0.5 more must fail when full.
+	if err := c.Add(0.5); err == nil {
+		t.Errorf("Add(0.5) on full category succeeded, want error")
+	}
+
+	// Remove 2.5 from the right (-2, -1, and half of 0).
+	if err := c.Remove(2.5); err != nil {
+		t.Fatalf("Remove(2.5) error = %v", err)
+	}
+	if got := c.Score(); got != 4.0 {
+		t.Errorf("Score() = %v, want 4.0", got)
+	}
+
+	// Removing more than remaining (3.5) must fail.
+	if err := c.Remove(4.0); err == nil {
+		t.Errorf("Remove(4.0) with 3.5 remaining succeeded, want error")
+	}
+}
diff --git a/internal/dqs/category/high-quality.go b/internal/dqs/category/high-quality.go
new file mode 100644
index 0000000..e7371f7
--- /dev/null
+++ b/internal/dqs/category/high-quality.go
@@ -0,0 +1,122 @@
+package category
+
+import "code.chimeric.al/dwrz/dqs/internal/dqs/portion"
+
+var (
+	Dairy = Category{
+		Name: "Dairy",
+		Portions: []portion.Portion{
+			{Points: 2},
+			{Points: 1},
+			{Points: 1},
+			{Points: 0},
+			{Points: -1},
+			{Points: -2},
+		},
+		HighQuality: true,
+	}
+
+	Fruit = Category{
+		Name: "Fruit",
+		Portions: []portion.Portion{
+			{Points: 2},
+			{Points: 2},
+			{Points: 2},
+			{Points: 1},
+			{Points: 0},
+			{Points: 0},
+		},
+		HighQuality: true,
+	}
+
+	HQBeverages = Category{
+		Name: "High Quality Beverages",
+		Portions: []portion.Portion{
+			{Points: 1},
+			{Points: 1},
+			{Points: 0},
+			{Points: 0},
+			{Points: -1},
+			{Points: -2},
+		},
+		HighQuality: true,
+	}
+
+	HQProcessedFoods = Category{
+		Name: "Processed Foods",
+		Portions: []portion.Portion{
+			{Points: 1},
+			{Points: 0},
+			{Points: -1},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+		},
+		HighQuality: true,
+	}
+
+	LegumesPlantProteins = Category{
+		Name: "Legumes & Plant Proteins",
+		Portions: []portion.Portion{
+			{Points: 2},
+			{Points: 2},
+			{Points: 1},
+			{Points: 0},
+			{Points: -1},
+			{Points: -1},
+		},
+		HighQuality: true,
+	}
+
+	NutsSeedsHealthyOils = Category{
+		Name: "Nuts, Seeds, Healthy Oils",
+		Portions: []portion.Portion{
+			{Points: 2},
+			{Points: 2},
+			{Points: 1},
+			{Points: 0},
+			{Points: 0},
+			{Points: -1},
+		},
+		HighQuality: true,
+	}
+
+	UnprocessedMeatSeafood = Category{
+		Name: "Unprocessed Meat & Seafood",
+		Portions: []portion.Portion{
+			{Points: 2},
+			{Points: 1},
+			{Points: 1},
+			{Points: 0},
+			{Points: -1},
+			{Points: -2},
+		},
+		HighQuality: true,
+	}
+
+	Vegetables = Category{
+		Name: "Vegetables",
+		Portions: []portion.Portion{
+			{Points: 2},
+			{Points: 2},
+			{Points: 2},
+			{Points: 1},
+			{Points: 0},
+			{Points: 0},
+		},
+		HighQuality: true,
+	}
+
+	WholeGrains = Category{
+		Name: "Whole Grains",
+		Portions: []portion.Portion{
+			{Points: 2},
+			{Points: 2},
+			{Points: 1},
+			{Points: 0},
+			{Points: 0},
+			{Points: -1},
+		},
+		HighQuality: true,
+	}
+)
diff --git a/internal/dqs/category/low-quality.go b/internal/dqs/category/low-quality.go
new file mode 100644
index 0000000..ffab3ed
--- /dev/null
+++ b/internal/dqs/category/low-quality.go
@@ -0,0 +1,84 @@
+package category
+
+import dqs "code.chimeric.al/dwrz/dqs/internal/dqs/portion"
+
+// Low Quality
+var (
+	FriedFoods = Category{
+		Name: "Fried Foods",
+		Portions: []dqs.Portion{
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+		},
+		HighQuality: false,
+	}
+
+	LQBeverages = Category{
+		Name: "Low Quality Beverages",
+		Portions: []dqs.Portion{
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+		},
+		HighQuality: false,
+	}
+
+	Other = Category{
+		Name: "Other",
+		Portions: []dqs.Portion{
+			{Points: -1},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+		},
+		HighQuality: false,
+	}
+
+	ProcessedMeat = Category{
+		Name: "Processed Meat",
+		Portions: []dqs.Portion{
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+		},
+		HighQuality: false,
+	}
+
+	RefinedGrains = Category{
+		Name: "Refined Grains",
+		Portions: []dqs.Portion{
+			{Points: -1},
+			{Points: -1},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+		},
+		HighQuality: false,
+	}
+
+	Sweets = Category{
+		Name: "Sweets",
+		Portions: []dqs.Portion{
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+			{Points: -2},
+		},
+		HighQuality: false,
+	}
+)
diff --git a/internal/dqs/command/add.go b/internal/dqs/command/add.go
new file mode 100644
index 0000000..d39cc13
--- /dev/null
+++ b/internal/dqs/command/add.go
@@ -0,0 +1,75 @@
+package command
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/portion"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+var Add = &command{
+	execute: addPortions,
+
+	description: "add portions to an entry",
+	help:        help.Add,
+	name:        "add",
+}
+
+func addPortions(args []string, date time.Time, store *store.Store) error {
+	u, err := store.GetUser()
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get user: %w", err)
+	}
+	if u == nil {
+		return Config.execute(args, date, store)
+	}
+
+	e, err := store.GetEntry(date.Format(entry.DateFormat))
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get entry: %w", err)
+	}
+	if e == nil {
+		e = entry.New(date, u)
+	}
+
+	if len(args) < 2 {
+		return fmt.Errorf("missing category and quantity")
+	}
+	if len(args)%2 != 0 {
+		return fmt.Errorf("uneven number of arguments")
+	}
+
+	for i := 0; i < len(args); i += 2 {
+		portionCategory := args[i]
+		quantity := args[i+1]
+
+		c, err := e.Category(portionCategory)
+		if err != nil {
+			return err
+		}
+
+		q, err := portion.Parse(quantity)
+		if err != nil {
+			return err
+		}
+
+		if err := c.Add(q); err != nil {
+			return fmt.Errorf(
+				"failed to add portions: %w", err,
+			)
+		}
+	}
+
+	if err := store.UpdateEntry(e); err != nil {
+		return fmt.Errorf("failed to store entry: %w", err)
+	}
+
+	fmt.Println(e.FormatPrint(u))
+
+	return nil
+}
diff --git a/internal/dqs/command/body-fat.go b/internal/dqs/command/body-fat.go
new file mode 100644
index 0000000..43e221c
--- /dev/null
+++ b/internal/dqs/command/body-fat.go
@@ -0,0 +1,68 @@
+package command
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+var BodyFat = &command{
+	execute: setBodyFat,
+
+	description: "set the user's body fat percentage on an entry",
+	help:        help.BodyFat,
+	name:        "body-fat",
+}
+
+func setBodyFat(args []string, date time.Time, store *store.Store) error {
+	u, err := store.GetUser()
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get user: %w", err)
+	}
+	if u == nil {
+		return Config.execute(args, date, store)
+	}
+
+	e, err := store.GetEntry(date.Format(entry.DateFormat))
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get entry: %w", err)
+	}
+	if e == nil {
+		e = entry.New(date, u)
+	}
+
+	if len(args) == 0 {
+		return fmt.Errorf("missing body fat percentage")
+	}
+
+	bf, err := strconv.ParseFloat(args[0], 64)
+	if err != nil {
+		return err
+	}
+
+	e.BodyFat = bf
+
+	if err := store.UpdateEntry(e); err != nil {
+		return fmt.Errorf("failed to store entry: %w", err)
+	}
+
+	// If the entry is for today, update the user.
+	var currentDate = time.Now().Format(entry.DateFormat)
+	if currentDate == date.Format(entry.DateFormat) {
+		u.BodyFat = bf
+
+		if err := store.UpdateUser(u); err != nil {
+			return fmt.Errorf("failed to store user: %w", err)
+		}
+	}
+
+	fmt.Println(u.FormatPrint())
+
+	return nil
+}
diff --git a/internal/dqs/command/command.go b/internal/dqs/command/command.go
new file mode 100644
index 0000000..c77a766
--- /dev/null
+++ b/internal/dqs/command/command.go
@@ -0,0 +1,53 @@
+package command
+
+import (
+	"fmt"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+type command struct {
+	execute func(args []string, date time.Time, store *store.Store) error
+
+	description string
+	help        func() string
+	name        string
+}
+
+func (c command) Execute(p Parameters) error {
+	if err := p.Validate(); err != nil {
+		return err
+	}
+
+	return c.execute(p.Args, p.Date, p.Store)
+}
+
+var commands []*command
+
+func init() {
+	commands = []*command{
+		Add,
+		BodyFat,
+		Config,
+		Delete,
+		Entry,
+		Export,
+		Help,
+		Note,
+		Remove,
+		Report,
+		User,
+		Weight,
+	}
+}
+
+func Match(name string) (*command, error) {
+	for _, command := range commands {
+		if name == command.name {
+			return command, nil
+		}
+	}
+
+	return nil, fmt.Errorf("unrecognized command: %s", name)
+}
diff --git a/internal/dqs/command/config.go b/internal/dqs/command/config.go
new file mode 100644
index 0000000..92cff87
--- /dev/null
+++ b/internal/dqs/command/config.go
@@ -0,0 +1,204 @@
+package command
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/diet"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user/units"
+	"code.chimeric.al/dwrz/dqs/pkg/color"
+)
+
+var Config = &command{
+	execute: configure,
+
+	description: "configure the user settings",
+	help:        help.Config,
+	name:        "config",
+}
+
+func configure(args []string, date time.Time, store *store.Store) error {
+	u, err := store.GetUser()
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return err
+	}
+	if u == nil {
+		defaultUser := user.DefaultUser
+		u = &defaultUser
+	}
+
+	fmt.Printf(
+		"%sPress enter to skip a field.%s\n",
+		color.Italic, color.Reset,
+	)
+
+	var in = bufio.NewReader(os.Stdin)
+
+	// Parse the name.
+	fmt.Print("Name: ")
+	line, err := in.ReadString('\n')
+	if err != nil {
+		return err
+	}
+
+	if line = strings.TrimSpace(line); line != "" {
+		u.Name = line
+	}
+
+	// Parse the birthday.
+	fmt.Print("Birthday (YYYYMMDD): ")
+	line, err = in.ReadString('\n')
+	if err != nil {
+		return err
+	}
+
+	if line = strings.TrimSpace(line); line != "" {
+		birthday, err := time.Parse("20060102", line)
+		if err != nil {
+			return err
+		}
+
+		u.Birthday = birthday
+	}
+
+	// Parse the units.
+	fmt.Print("Units (imperial|metric): ")
+	line, err = in.ReadString('\n')
+	if err != nil {
+		return err
+	}
+
+	if line = strings.TrimSpace(line); line != "" {
+		system := units.System(line)
+
+		if !units.Valid(system) {
+			return fmt.Errorf("invalid units")
+		}
+
+		u.Units = system
+	}
+
+	// Parse the height.
+	fmt.Printf("Height (%s): ", u.Units.Height())
+	line, err = in.ReadString('\n')
+	if err != nil {
+		return err
+	}
+
+	if line = strings.TrimSpace(line); line != "" {
+		height, err := strconv.ParseFloat(line, 64)
+		if err != nil {
+			return err
+		}
+		if height < 0 {
+			return fmt.Errorf("invalid height")
+		}
+
+		// Store all units in metric.
+		if u.Units == units.Imperial {
+			height = units.InchesToCentimeter(height)
+		}
+
+		u.Height = height
+	}
+
+	// Parse the weight.
+	fmt.Printf("Weight (%s): ", u.Units.Weight())
+	line, err = in.ReadString('\n')
+	if err != nil {
+		return err
+	}
+
+	if line = strings.TrimSpace(line); line != "" {
+		weight, err := strconv.ParseFloat(line, 64)
+		if err != nil {
+			return err
+		}
+		if weight < 0 {
+			return fmt.Errorf("invalid weight")
+		}
+
+		// Store all units in metric.
+		if u.Units == units.Imperial {
+			weight = units.PoundsToKilogram(weight)
+		}
+
+		u.Weight = weight
+	}
+
+	// Parse the body fat.
+	fmt.Print("Body Fat (%): ")
+	line, err = in.ReadString('\n')
+	if err != nil {
+		return err
+	}
+
+	if line = strings.TrimSpace(line); line != "" {
+		bf, err := strconv.ParseFloat(line, 64)
+		if err != nil {
+			return err
+		}
+
+		if bf < 0 || bf > 100 {
+			return fmt.Errorf("invalid body fat percentage")
+		}
+
+		u.BodyFat = bf
+	}
+
+	// Parse the diet.
+	fmt.Print("Diet (omnivore|vegan|vegetarian): ")
+	line, err = in.ReadString('\n')
+	if err != nil {
+		return err
+	}
+
+	if line = strings.TrimSpace(line); line != "" {
+		if !diet.Valid(diet.Diet(line)) {
+			return fmt.Errorf("unrecognized diet")
+		}
+
+		u.Diet = diet.Diet(line)
+	}
+
+	// Parse the Target Weight.
+	fmt.Printf("Target Weight (%s): ", u.Units.Weight())
+	line, err = in.ReadString('\n')
+	if err != nil {
+		return err
+	}
+
+	if line = strings.TrimSpace(line); line != "" {
+		tw, err := strconv.ParseFloat(line, 64)
+		if err != nil {
+			return err
+		}
+
+		if tw < 0 {
+			return fmt.Errorf("invalid target weight")
+		}
+
+		// Store all units in metric.
+		if u.Units == units.Imperial {
+			tw = units.PoundsToKilogram(tw)
+		}
+
+		u.TargetWeight = tw
+	}
+
+	if err := store.UpdateUser(u); err != nil {
+		return fmt.Errorf(
+			"failed to store user: %w", err,
+		)
+	}
+
+	return nil
+}
diff --git a/internal/dqs/command/delete.go b/internal/dqs/command/delete.go
new file mode 100644
index 0000000..fd737bc
--- /dev/null
+++ b/internal/dqs/command/delete.go
@@ -0,0 +1,26 @@
+package command
+
+import (
+	"fmt"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+var Delete = &command{
+	execute: func(args []string, date time.Time, store *store.Store) error {
+		id := date.Format(entry.DateFormat)
+
+		if err := store.DeleteEntry(id); err != nil {
+			return fmt.Errorf("failed to delete entry: %w", err)
+		}
+
+		return nil
+	},
+
+	description: "delete an entry",
+	help:        help.Delete,
+	name:        "delete",
+}
diff --git a/internal/dqs/command/entry.go b/internal/dqs/command/entry.go
new file mode 100644
index 0000000..1237b6f
--- /dev/null
+++ b/internal/dqs/command/entry.go
@@ -0,0 +1,40 @@
+package command
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+var Entry = &command{
+	execute: func(args []string, date time.Time, store *store.Store) error {
+		u, err := store.GetUser()
+		if err != nil && !errors.Is(err, os.ErrNotExist) {
+			return fmt.Errorf("failed to get user: %w", err)
+		}
+		if u == nil {
+			return Config.execute(args, date, store)
+		}
+
+		e, err := store.GetEntry(date.Format(entry.DateFormat))
+		if err != nil && !errors.Is(err, os.ErrNotExist) {
+			return fmt.Errorf("failed to get entry: %w", err)
+		}
+		if e == nil {
+			e = entry.New(date, u)
+		}
+
+		fmt.Println(e.FormatPrint(u))
+
+		return nil
+	},
+
+	description: "display a date's entry (default)",
+	help:        help.Entry,
+	name:        "entry",
+}
diff --git a/internal/dqs/command/export.go b/internal/dqs/command/export.go
new file mode 100644
index 0000000..e4d57d3
--- /dev/null
+++ b/internal/dqs/command/export.go
@@ -0,0 +1,40 @@
+package command
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+var Export = &command{
+	execute: func(args []string, date time.Time, store *store.Store) error {
+		entries, err := store.GetAllEntries()
+		if err != nil {
+			return err
+		}
+
+		var str strings.Builder
+		str.WriteString("date,body-fat,dqs,weight,\n")
+
+		for _, e := range entries {
+			str.WriteString(fmt.Sprintf(
+				"%s,%.2f,%.1f,%.2f,\n",
+				e.Date.Format("20060102"),
+				e.BodyFat,
+				e.Score(),
+				e.Weight,
+			))
+		}
+
+		fmt.Println(str.String())
+
+		return nil
+	},
+
+	description: "export entries to csv",
+	help:        help.Export,
+	name:        "export",
+}
diff --git a/internal/dqs/command/help.go b/internal/dqs/command/help.go
new file mode 100644
index 0000000..193639b
--- /dev/null
+++ b/internal/dqs/command/help.go
@@ -0,0 +1,63 @@
+package command
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+const (
+	helpIntro = `dqs — diet quality score
+
+Usage:
+	dqs [flags] <command> [arguments]
+
+
+Run dqs -help or dqs -h to see information on available flags.
+
+The following commands are available:
+
+`
+	helpMore = "Run dqs help <command> to see the command's documentation."
+)
+
+var Help = &command{
+	execute: showHelp,
+
+	description: "show built-in command documentation",
+	help:        help.Help,
+	name:        "help",
+}
+
+func showHelp(args []string, date time.Time, store *store.Store) error {
+	if len(args) == 0 {
+		var str strings.Builder
+
+		str.WriteString(helpIntro)
+
+		for _, c := range commands {
+			str.WriteString(
+				fmt.Sprintf("%-11s%s\n", c.name, c.description),
+			)
+		}
+
+		str.WriteString("\n")
+		str.WriteString(helpMore)
+
+		fmt.Println(str.String())
+
+		return nil
+	}
+
+	cmd, err := Match(args[0])
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(cmd.help())
+
+	return nil
+}
diff --git a/internal/dqs/command/help/add.go b/internal/dqs/command/help/add.go
new file mode 100644
index 0000000..3da2d7d
--- /dev/null
+++ b/internal/dqs/command/help/add.go
@@ -0,0 +1,34 @@
+package help
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/category"
+)
+
+var add = strings.ReplaceAll(portions, "%s", "add")
+
+func Add() string {
+	var str strings.Builder
+
+	str.WriteString(add)
+
+	var abbreviations = [][2]string{}
+	for abbreviation, name := range category.Abbreviations {
+		abbreviations = append(abbreviations, [2]string{
+			name, abbreviation,
+		})
+	}
+
+	sort.Slice(abbreviations, func(i, j int) bool {
+		return abbreviations[i][0] < abbreviations[j][0]
+	})
+
+	for _, a := range abbreviations {
+		str.WriteString(fmt.Sprintf("%-5s %s\n", a[1], a[0]))
+	}
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/body-fat.go b/internal/dqs/command/help/body-fat.go
new file mode 100644
index 0000000..eeb51a2
--- /dev/null
+++ b/internal/dqs/command/help/body-fat.go
@@ -0,0 +1,24 @@
+package help
+
+import "strings"
+
+const bodyFat = `The body-fat command sets the body fat percentage on an entry.
+
+It accepts a single argument, a number which represents the body fat
+percentage. The number may have a decimal component.
+
+If the date used is the current date, your user data will also be
+updated to use the body fat percentage. This will default future entries
+to the inputted percentage.
+
+Example:
+dqs body-fat 24.25
+`
+
+func BodyFat() string {
+	var str strings.Builder
+
+	str.WriteString(bodyFat)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/config.go b/internal/dqs/command/help/config.go
new file mode 100644
index 0000000..129b5e2
--- /dev/null
+++ b/internal/dqs/command/help/config.go
@@ -0,0 +1,33 @@
+package help
+
+import "strings"
+
+const config = `The config command is used to configure dqs.
+
+It allows for entry of the following fields:
+
+Name
+Birthday
+Units (imperial or metric*)
+Height
+Weight
+Body Fat Percentage
+Diet (omnivore, vegan, or vegetarian*)
+Target Weight
+
+All fields are optional. Units default to metric; the default diet is
+vegetarian.
+
+This command will be invoked automatically the first time dqs is run.
+
+Example:
+dqs config
+`
+
+func Config() string {
+	var str strings.Builder
+
+	str.WriteString(config)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/delete.go b/internal/dqs/command/help/delete.go
new file mode 100644
index 0000000..6cb4979
--- /dev/null
+++ b/internal/dqs/command/help/delete.go
@@ -0,0 +1,26 @@
+package help
+
+import "strings"
+
+const deleteEntry = `The delete command deletes an entry.
+
+The entry date is specified via the -date flag (run dqs -help to read
+more about the flag).
+
+There are no arguments.
+
+There is no way to undo a deletion.
+
+The command returns an error if no entry exists for the specified date.
+
+Example:
+dqs -date 20210620 delete
+`
+
+func Delete() string {
+	var str strings.Builder
+
+	str.WriteString(deleteEntry)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/entry.go b/internal/dqs/command/help/entry.go
new file mode 100644
index 0000000..c1f216a
--- /dev/null
+++ b/internal/dqs/command/help/entry.go
@@ -0,0 +1,25 @@
+package help
+
+import "strings"
+
+const entry = `The entry command displays the date's entry.
+
+It is the default command run, if no command is specified.
+
+The entry date is specified via the -date flag (run dqs -help to read
+more about the flag).
+
+Example:
+dqs entry
+
+The command is equivalent to:
+dqs
+`
+
+func Entry() string {
+	var str strings.Builder
+
+	str.WriteString(entry)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/export.go b/internal/dqs/command/help/export.go
new file mode 100644
index 0000000..6941e32
--- /dev/null
+++ b/internal/dqs/command/help/export.go
@@ -0,0 +1,21 @@
+package help
+
+import "strings"
+
+const export = `The export command prints statistics from all entries.
+
+The columns are date, body-fat, diet quality score, and weight.
+
+The export format is Comma Separate Values (CSV).
+
+Example:
+dqs export
+`
+
+func Export() string {
+	var str strings.Builder
+
+	str.WriteString(export)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/help.go b/internal/dqs/command/help/help.go
new file mode 100644
index 0000000..37537e4
--- /dev/null
+++ b/internal/dqs/command/help/help.go
@@ -0,0 +1,39 @@
+package help
+
+import "strings"
+
+const help = `dqs is designed to help you keep track of your Diet
+Quality Score, as well as your progress on reaching a target weight.
+
+The typical use case is to use the *add* command to keep track of
+portions consumed. By default the application uses the current day, but
+if you need to catch up on a past date, the -d or -date flags can be
+used to refer to a past date or entry. For example, if you want to add
+two fruit portions for today, you can run:
+
+dqs add fruit 2
+
+To do the same for a past date -- for example, August 8, 2008 -- you
+can run:
+
+dqs -date 20080808 fruit 2
+
+or
+
+dqs -d 20080808 fruit 2
+
+Refer to dqs help add for more information on the *add* command.
+
+Weight and body fat may be tracked with the body-fat and weight
+commands.
+
+To check on progress towards goals, use the dqs report command.
+`
+
+func Help() string {
+	var str strings.Builder
+
+	str.WriteString(help)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/note.go b/internal/dqs/command/help/note.go
new file mode 100644
index 0000000..76e35fd
--- /dev/null
+++ b/internal/dqs/command/help/note.go
@@ -0,0 +1,33 @@
+package help
+
+import "strings"
+
+const note = `The note command is used to set a note on an entry.
+
+There are four subcommands available:
+
+append — used to add text to a note.
+
+delete — used to delete a note.
+
+edit — used to edit a note with a text editor (specified by the EDITOR
+environment variable).
+
+set — used to set (or overwrite) a note.
+
+If not subcommand is specified, the entry's note is displayed.
+
+Examples:
+dqs note append Hello World
+dqs -date 20111111 note delete
+dqs note edit
+dqs note set This is a note.
+`
+
+func Note() string {
+	var str strings.Builder
+
+	str.WriteString(note)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/portions.go b/internal/dqs/command/help/portions.go
new file mode 100644
index 0000000..62afaeb
--- /dev/null
+++ b/internal/dqs/command/help/portions.go
@@ -0,0 +1,32 @@
+package help
+
+const portions = `The %s command %ss portions to an entry.
+
+It accepts pairs of arguments -- a category name followed by a portion
+amount.
+
+For example:
+dqs %s fruit 1
+
+This will %s one portion to the Fruit category.
+
+It is possible to specify a half portion, e.g.:
+dqs %s vegetables 2.5
+
+Will %s 2½ portions to the Vegetable category.
+
+It is also possible to specify multiple pairs of arguments, e.g.:
+dqs %s dairy 1 "Whole Grains" 2
+
+This will %s 1 dairy portion, and 2 whole grain portions to an entry.
+Note that category names may be cased in any manner, but names with
+a space in them must be quoted, as in the "Whole Grains" example above.
+
+To reduce typing, abbreviations are available for category names, e.g.:
+dqs %s d 1 hqb 1 v 2 wg 1.5
+
+Will %s 1 portion of dairy, 1 portion of high quality beverages, 2
+portions of vegetables, and 1½ portions of whole grains.
+
+The following abbreviations are available:
+`
diff --git a/internal/dqs/command/help/remove.go b/internal/dqs/command/help/remove.go
new file mode 100644
index 0000000..73315e3
--- /dev/null
+++ b/internal/dqs/command/help/remove.go
@@ -0,0 +1,34 @@
+package help
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/category"
+)
+
+var remove = strings.ReplaceAll(portions, "%s", "remove")
+
+func Remove() string {
+	var str strings.Builder
+
+	str.WriteString(remove)
+
+	var abbreviations = [][2]string{}
+	for abbreviation, name := range category.Abbreviations {
+		abbreviations = append(abbreviations, [2]string{
+			name, abbreviation,
+		})
+	}
+
+	sort.Slice(abbreviations, func(i, j int) bool {
+		return abbreviations[i][0] < abbreviations[j][0]
+	})
+
+	for _, a := range abbreviations {
+		str.WriteString(fmt.Sprintf("%-5s %s\n", a[1], a[0]))
+	}
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/report.go b/internal/dqs/command/help/report.go
new file mode 100644
index 0000000..2abcb85
--- /dev/null
+++ b/internal/dqs/command/help/report.go
@@ -0,0 +1,25 @@
+package help
+
+import "strings"
+
+const report = `The report command displays a report on your statistics
+and usage.
+
+The command will display the statistics on the following:
+
+Entries
+Body Fat
+DQS
+Weight
+
+It will also display recommendations as to which food categories you
+should eat more or less of, given past entries.
+`
+
+func Report() string {
+	var str strings.Builder
+
+	str.WriteString(report)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/user.go b/internal/dqs/command/help/user.go
new file mode 100644
index 0000000..fab7c79
--- /dev/null
+++ b/internal/dqs/command/help/user.go
@@ -0,0 +1,20 @@
+package help
+
+import "strings"
+
+const user = `The user command displays your user data.
+
+This command may be used to confirm settings -- such as diet -- or the
+user's current measurements -- such as height and weight.
+
+Example:
+dqs user
+`
+
+func User() string {
+	var str strings.Builder
+
+	str.WriteString(user)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/help/weight.go b/internal/dqs/command/help/weight.go
new file mode 100644
index 0000000..aeba414
--- /dev/null
+++ b/internal/dqs/command/help/weight.go
@@ -0,0 +1,23 @@
+package help
+
+import "strings"
+
+const weight = `The weight command sets your weight on an entry.
+
+It accepts a single argument, a number which represents your weight.
+The number may have a decimal component.
+
+If the date used is the current date, your user data will also be updated.
+This will default future entries to the inputted weight.
+
+Example:
+dqs weight 100.00
+`
+
+func Weight() string {
+	var str strings.Builder
+
+	str.WriteString(weight)
+
+	return str.String()
+}
diff --git a/internal/dqs/command/note.go b/internal/dqs/command/note.go
new file mode 100644
index 0000000..645cc03
--- /dev/null
+++ b/internal/dqs/command/note.go
@@ -0,0 +1,135 @@
+package command
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+var Note = &command{
+	execute: setNote,
+
+	description: "set a note on an entry",
+	help:        help.Note,
+	name:        "note",
+}
+
+func setNote(args []string, date time.Time, store *store.Store) error {
+	u, err := store.GetUser()
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get user: %w", err)
+	}
+	if u == nil {
+		return Config.execute(args, date, store)
+	}
+
+	e, err := store.GetEntry(date.Format(entry.DateFormat))
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get entry: %w", err)
+	}
+	if e == nil {
+		e = entry.New(date, u)
+	}
+
+	if len(args) == 0 {
+		fmt.Println(e.Note)
+
+		return nil
+	}
+
+	update, args := args[0], args[1:]
+	switch update {
+	case "append":
+		if len(args) >= 1 {
+			if len(e.Note) == 0 {
+				e.Note = strings.Join(args, " ")
+			} else {
+				e.Note = fmt.Sprintf(
+					"%s\n%s", e.Note,
+					strings.Join(args, " "),
+				)
+			}
+		}
+
+	case "delete":
+		e.Note = ""
+
+	case "edit":
+		var err error
+		e.Note, err = editNote(e.Note)
+		if err != nil {
+			return err
+		}
+
+	case "set":
+		if len(args) >= 1 {
+			e.Note = strings.Join(args, " ")
+		}
+
+	default:
+		fmt.Println(e.Note)
+	}
+
+	if err := store.UpdateEntry(e); err != nil {
+		return fmt.Errorf("failed to store entry: %w", err)
+	}
+
+	return nil
+}
+
+func editNote(note string) (string, error) {
+	editor := strings.TrimSpace(os.Getenv("EDITOR"))
+	if editor == "" {
+		return "", fmt.Errorf("$EDITOR is not set")
+	}
+
+	// Write the note to a temporary file for the external editor.
+	temp, err := os.CreateTemp(os.TempDir(), "dqs-*")
+	if err != nil {
+		return "", err
+	}
+	defer os.Remove(temp.Name())
+
+	if _, err := temp.Write([]byte(note)); err != nil {
+		temp.Close()
+		return "", err
+	}
+	if err := temp.Close(); err != nil {
+		return "", err
+	}
+
+	args := strings.Fields(editor)
+	args = append(args, temp.Name())
+
+	path, err := exec.LookPath(args[0])
+	if err != nil {
+		return "", fmt.Errorf(
+			"failed to find $EDITOR %s: %w", editor, err,
+		)
+	}
+
+	cmd := exec.Cmd{
+		Path:   path,
+		Args:   args,
+		Stdin:  os.Stdin,
+		Stdout: os.Stdout,
+		Stderr: os.Stderr,
+	}
+	if err := cmd.Run(); err != nil {
+		return "", err
+	}
+
+	data, err := os.ReadFile(temp.Name())
+	if err != nil {
+		return "", err
+	}
+
+	return string(data), nil
+}
diff --git a/internal/dqs/command/parameters.go b/internal/dqs/command/parameters.go
new file mode 100644
index 0000000..cc8584d
--- /dev/null
+++ b/internal/dqs/command/parameters.go
@@ -0,0 +1,25 @@
+package command
+
+import (
+	"fmt"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+type Parameters struct {
+	Args  []string
+	Date  time.Time
+	Store *store.Store
+}
+
+func (p *Parameters) Validate() error {
+	if p.Args == nil {
+		return fmt.Errorf("missing arguments")
+	}
+	if p.Store == nil {
+		return fmt.Errorf("missing store")
+	}
+
+	return nil
+}
diff --git a/internal/dqs/command/remove.go b/internal/dqs/command/remove.go
new file mode 100644
index 0000000..c6cb0a5
--- /dev/null
+++ b/internal/dqs/command/remove.go
@@ -0,0 +1,75 @@
+package command
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/portion"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+var Remove = &command{
+	execute: removePortions,
+
+	description: "remove portions from an entry",
+	help:        help.Remove,
+	name:        "remove",
+}
+
+func removePortions(args []string, date time.Time, store *store.Store) error {
+	u, err := store.GetUser()
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get user: %w", err)
+	}
+	if u == nil {
+		return Config.execute(args, date, store)
+	}
+
+	e, err := store.GetEntry(date.Format(entry.DateFormat))
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get entry: %w", err)
+	}
+	if e == nil {
+		e = entry.New(date, u)
+	}
+
+	if len(args) < 2 {
+		return fmt.Errorf("missing category and quantity")
+	}
+	if len(args)%2 != 0 {
+		return fmt.Errorf("uneven number of arguments")
+	}
+
+	for i := 0; i < len(args); i += 2 {
+		portionCategory := args[i]
+		quantity := args[i+1]
+
+		c, err := e.Category(portionCategory)
+		if err != nil {
+			return err
+		}
+
+		q, err := portion.Parse(quantity)
+		if err != nil {
+			return err
+		}
+
+		if err := c.Remove(q); err != nil {
+			return fmt.Errorf(
+				"failed to remove portions: %w", err,
+			)
+		}
+	}
+
+	if err := store.UpdateEntry(e); err != nil {
+		return fmt.Errorf("failed to store entry: %w", err)
+	}
+
+	fmt.Println(e.FormatPrint(u))
+
+	return nil
+}
diff --git a/internal/dqs/command/report.go b/internal/dqs/command/report.go
new file mode 100644
index 0000000..74179b3
--- /dev/null
+++ b/internal/dqs/command/report.go
@@ -0,0 +1,27 @@
+package command
+
+import (
+	"fmt"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/report"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+var Report = &command{
+	execute: func(args []string, date time.Time, store *store.Store) error {
+		entries, err := store.GetAllEntries()
+		if err != nil {
+			return err
+		}
+
+		fmt.Println(report.New(entries).Format())
+
+		return nil
+	},
+
+	description: "report user and entry statistics",
+	help:        help.Report,
+	name:        "report",
+}
diff --git a/internal/dqs/command/user.go b/internal/dqs/command/user.go
new file mode 100644
index 0000000..d27efb1
--- /dev/null
+++ b/internal/dqs/command/user.go
@@ -0,0 +1,31 @@
+package command
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+var User = &command{
+	execute: func(args []string, date time.Time, store *store.Store) error {
+		u, err := store.GetUser()
+		if err != nil && !errors.Is(err, os.ErrNotExist) {
+			return fmt.Errorf("failed to get user: %w", err)
+		}
+		if u == nil {
+			return Config.execute(args, date, store)
+		}
+
+		fmt.Println(u.FormatPrint())
+
+		return nil
+	},
+
+	description: "display user data and settings",
+	help:        help.User,
+	name:        "user",
+}
diff --git a/internal/dqs/command/weight.go b/internal/dqs/command/weight.go
new file mode 100644
index 0000000..567cf29
--- /dev/null
+++ b/internal/dqs/command/weight.go
@@ -0,0 +1,74 @@
+package command
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command/help"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user/units"
+)
+
+var Weight = &command{
+	execute: setWeight,
+
+	description: "set the user's weight on an entry",
+	help:        help.Weight,
+	name:        "weight",
+}
+
+func setWeight(args []string, date time.Time, store *store.Store) error {
+	u, err := store.GetUser()
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get user: %w", err)
+	}
+	if u == nil {
+		return Config.execute(args, date, store)
+	}
+
+	e, err := store.GetEntry(date.Format(entry.DateFormat))
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to get entry: %w", err)
+	}
+	if e == nil {
+		e = entry.New(date, u)
+	}
+
+	if len(args) == 0 {
+		return fmt.Errorf("missing weight")
+	}
+
+	w, err := strconv.ParseFloat(args[0], 64)
+	if err != nil {
+		return err
+	}
+
+	// Store all units in metric.
+	if u.Units == units.Imperial {
+		w = units.PoundsToKilogram(w)
+	}
+
+	e.Weight = w
+
+	if err := store.UpdateEntry(e); err != nil {
+		return fmt.Errorf("failed to store entry: %w", err)
+	}
+
+	// If the entry is for today, update the user.
+	var currentDate = time.Now().Format(entry.DateFormat)
+	if currentDate == date.Format(entry.DateFormat) {
+		u.Weight = w
+
+		if err := store.UpdateUser(u); err != nil {
+			return fmt.Errorf("failed to store user: %w", err)
+		}
+	}
+
+	fmt.Println(u.FormatPrint())
+
+	return nil
+}
diff --git a/internal/dqs/diet/diet.go b/internal/dqs/diet/diet.go
new file mode 100644
index 0000000..877f0d8
--- /dev/null
+++ b/internal/dqs/diet/diet.go
@@ -0,0 +1,67 @@
+package diet
+
+import (
+	"code.chimeric.al/dwrz/dqs/internal/dqs/category"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/portion"
+)
+
+type Diet string
+
+const (
+	Omnivore   Diet = "omnivore"
+	Vegan      Diet = "vegan"
+	Vegetarian Diet = "vegetarian"
+)
+
+func Valid(d Diet) bool {
+	switch d {
+	case Omnivore, Vegan, Vegetarian:
+		return true
+	default:
+		return false
+	}
+}
+
+// Template returns a fresh category map for the diet.
+// Each category and its portion slice are copied so mutations on an entry do
+// not modify the package-level template definitions.
+func (d Diet) Template() map[string]*category.Category {
+	var src map[string]category.Category
+	switch d {
+	case Omnivore:
+		src = omnivore
+	case Vegan:
+		src = vegan
+	case Vegetarian:
+		src = vegetarian
+	default:
+		return nil
+	}
+
+	var tmpl = make(map[string]*category.Category, len(src))
+	for name, c := range src {
+		portions := make([]portion.Portion, len(c.Portions))
+		copy(portions, c.Portions)
+		c.Portions = portions
+		tmpl[name] = &c
+	}
+
+	return tmpl
+}
+
+// MaxScore returns the maximum possible score for the diet, calculated as the
+// sum of all positive portion points across the diet's categories.
+func (d Diet) MaxScore() int {
+	tmpl := d.Template()
+
+	var max int
+	for _, category := range tmpl {
+		for _, portion := range category.Portions {
+			if portion.Points > 0 {
+				max += portion.Points
+			}
+		}
+	}
+
+	return max
+}
diff --git a/internal/dqs/diet/omnivore.go b/internal/dqs/diet/omnivore.go
new file mode 100644
index 0000000..d6cba56
--- /dev/null
+++ b/internal/dqs/diet/omnivore.go
@@ -0,0 +1,23 @@
+package diet
+
+import "code.chimeric.al/dwrz/dqs/internal/dqs/category"
+
+var omnivore = map[string]category.Category{
+	// High Quality
+	category.Dairy.Name:                  category.Dairy,
+	category.Fruit.Name:                  category.Fruit,
+	category.HQBeverages.Name:            category.HQBeverages,
+	category.HQProcessedFoods.Name:       category.HQProcessedFoods,
+	category.NutsSeedsHealthyOils.Name:   category.NutsSeedsHealthyOils,
+	category.UnprocessedMeatSeafood.Name: category.UnprocessedMeatSeafood,
+	category.Vegetables.Name:             category.Vegetables,
+	category.WholeGrains.Name:            category.WholeGrains,
+
+	// Low Quality
+	category.FriedFoods.Name:    category.FriedFoods,
+	category.LQBeverages.Name:   category.LQBeverages,
+	category.Other.Name:         category.Other,
+	category.ProcessedMeat.Name: category.ProcessedMeat,
+	category.RefinedGrains.Name: category.RefinedGrains,
+	category.Sweets.Name:        category.Sweets,
+}
diff --git a/internal/dqs/diet/vegan.go b/internal/dqs/diet/vegan.go
new file mode 100644
index 0000000..40f477e
--- /dev/null
+++ b/internal/dqs/diet/vegan.go
@@ -0,0 +1,21 @@
+package diet
+
+import "code.chimeric.al/dwrz/dqs/internal/dqs/category"
+
+var vegan = map[string]category.Category{
+	// High Quality
+	category.Fruit.Name:                category.Fruit,
+	category.HQBeverages.Name:          category.HQBeverages,
+	category.HQProcessedFoods.Name:     category.HQProcessedFoods,
+	category.LegumesPlantProteins.Name: category.LegumesPlantProteins,
+	category.NutsSeedsHealthyOils.Name: category.NutsSeedsHealthyOils,
+	category.Vegetables.Name:           category.Vegetables,
+	category.WholeGrains.Name:          category.WholeGrains,
+
+	// Low Quality
+	category.FriedFoods.Name:    category.FriedFoods,
+	category.LQBeverages.Name:   category.LQBeverages,
+	category.Other.Name:         category.Other,
+	category.RefinedGrains.Name: category.RefinedGrains,
+	category.Sweets.Name:        category.Sweets,
+}
diff --git a/internal/dqs/diet/vegetarian.go b/internal/dqs/diet/vegetarian.go
new file mode 100644
index 0000000..18b8b47
--- /dev/null
+++ b/internal/dqs/diet/vegetarian.go
@@ -0,0 +1,22 @@
+package diet
+
+import "code.chimeric.al/dwrz/dqs/internal/dqs/category"
+
+var vegetarian = map[string]category.Category{
+	// High Quality
+	category.Dairy.Name:                category.Dairy,
+	category.Fruit.Name:                category.Fruit,
+	category.HQBeverages.Name:          category.HQBeverages,
+	category.HQProcessedFoods.Name:     category.HQProcessedFoods,
+	category.LegumesPlantProteins.Name: category.LegumesPlantProteins,
+	category.NutsSeedsHealthyOils.Name: category.NutsSeedsHealthyOils,
+	category.Vegetables.Name:           category.Vegetables,
+	category.WholeGrains.Name:          category.WholeGrains,
+
+	// Low Quality
+	category.FriedFoods.Name:    category.FriedFoods,
+	category.LQBeverages.Name:   category.LQBeverages,
+	category.Other.Name:         category.Other,
+	category.RefinedGrains.Name: category.RefinedGrains,
+	category.Sweets.Name:        category.Sweets,
+}
diff --git a/internal/dqs/dqs.go b/internal/dqs/dqs.go
new file mode 100644
index 0000000..3453fe1
--- /dev/null
+++ b/internal/dqs/dqs.go
@@ -0,0 +1,63 @@
+package dqs
+
+import (
+	"fmt"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/command"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/store"
+)
+
+type Config struct {
+	Dir string
+}
+
+func (c *Config) Validate() error {
+	if c.Dir == "" {
+		return fmt.Errorf("missing dqs directory")
+	}
+
+	return nil
+}
+
+type Command struct {
+	store *store.Store
+}
+
+func New(cfg Config) (*Command, error) {
+	if err := cfg.Validate(); err != nil {
+		return nil, err
+	}
+
+	store, err := store.Open(cfg.Dir)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Command{
+		store: store,
+	}, nil
+}
+
+func (a *Command) Run(args []string, date time.Time) error {
+	params := command.Parameters{
+		Args:  args,
+		Date:  date,
+		Store: a.store,
+	}
+
+	// If no arguments were provided, print the entry.
+	if len(args) == 0 {
+		return command.Entry.Execute(params)
+	}
+
+	// Process the command.
+	params.Args = args[1:]
+
+	cmd, err := command.Match(args[0])
+	if err != nil {
+		return err
+	}
+
+	return cmd.Execute(params)
+}
diff --git a/internal/dqs/entry/entry.go b/internal/dqs/entry/entry.go
new file mode 100644
index 0000000..abca05b
--- /dev/null
+++ b/internal/dqs/entry/entry.go
@@ -0,0 +1,78 @@
+package entry
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/category"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/diet"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user"
+)
+
+const (
+	DateFormat        = "20060102"
+	dateDisplayFormat = "2006-01-02"
+)
+
+// Entry holds the diet log and body measurements for a single calendar date.
+// Height and Weight are stored in metric units (cm and kg).
+type Entry struct {
+	BodyFat    float64                       `json:"bodyFat"`
+	Categories map[string]*category.Category `json:"categories"`
+	Date       time.Time                     `json:"date"`
+	Diet       diet.Diet                     `json:"diet"`
+	Height     float64                       `json:"height"`
+	Note       string                        `json:"note"`
+	Weight     float64                       `json:"weight"`
+}
+
+// New creates an entry initialized with the category template for the user's
+// diet. If date is today, the entry inherits the user's current body fat,
+// height, and weight; entries for other dates start with zero measurements.
+func New(date time.Time, u *user.User) *Entry {
+	var e = &Entry{
+		Categories: u.Diet.Template(),
+		Date:       date,
+		Diet:       u.Diet,
+	}
+
+	var currentDate = time.Now().Format(DateFormat)
+	if currentDate == date.Format(DateFormat) {
+		e.BodyFat = u.BodyFat
+		e.Height = u.Height
+		e.Weight = u.Weight
+	}
+
+	return e
+}
+
+// Key returns the key used to retrieve an entry from the store.
+func (e *Entry) Key() string {
+	return e.Date.Format(DateFormat)
+}
+
+// Score returns the total Diet Quality Score across all categories in the entry.
+func (e *Entry) Score() (total float64) {
+	for _, c := range e.Categories {
+		total += c.Score()
+	}
+
+	return total
+}
+
+// Category looks up a category by abbreviation or case-insensitive name.
+func (e *Entry) Category(c string) (*category.Category, error) {
+	// Try expanding an abbreviation.
+	if cat, exists := e.Categories[category.Abbreviations[c]]; exists {
+		return cat, nil
+	}
+	// Check if a category name was used (case-insensitive).
+	for name, cat := range e.Categories {
+		if strings.EqualFold(name, c) {
+			return cat, nil
+		}
+	}
+
+	return nil, fmt.Errorf("category %s not found", c)
+}
diff --git a/internal/dqs/entry/format.go b/internal/dqs/entry/format.go
new file mode 100644
index 0000000..008bca9
--- /dev/null
+++ b/internal/dqs/entry/format.go
@@ -0,0 +1,157 @@
+package entry
+
+import (
+	"fmt"
+
+	"sort"
+	"strconv"
+	"strings"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/category"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/stats"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user"
+	"code.chimeric.al/dwrz/dqs/pkg/color"
+)
+
+const (
+	width  = 44
+	top    = "┌────────────────────────────────────────────┐\n"
+	hr     = "├────────────────────────────────────────────┤\n"
+	bottom = "└────────────────────────────────────────────┘\n"
+)
+
+func centerPad(s string, width int) string {
+	return fmt.Sprintf(
+		"%[1]*s", -width, fmt.Sprintf("%[1]*s", (width+len(s))/2, s),
+	)
+}
+
+// FormatPrint formats an entry for display to the user.
+func (e *Entry) FormatPrint(u *user.User) string {
+	// Assemble the data for display.
+	var (
+		highQuality []*category.Category
+		lowQuality  []*category.Category
+	)
+
+	// Separate high quality and low quality categories.
+	for _, c := range e.Categories {
+		if c.HighQuality {
+			highQuality = append(highQuality, c)
+			continue
+		}
+		lowQuality = append(lowQuality, c)
+	}
+
+	// Sort alphabetically for consistent appearance.
+	sort.Slice(highQuality, func(i, j int) bool {
+		return highQuality[i].Name < highQuality[j].Name
+	})
+	sort.Slice(lowQuality, func(i, j int) bool {
+		return lowQuality[i].Name < lowQuality[j].Name
+	})
+
+	// Prepare a string for display to the user.
+	var str strings.Builder
+
+	// Format the date.
+	str.WriteString(top)
+	str.WriteString(fmt.Sprintf(
+		"│%s%s%s│\n",
+		color.BrightBlack,
+		centerPad(e.Date.Format(dateDisplayFormat), width),
+		color.Reset,
+	))
+	str.WriteString(hr)
+
+	// Format high-quality categories.
+	str.WriteString(fmt.Sprintf("│%-44s│\n", "High Quality"))
+	str.WriteString(hr)
+	for _, c := range highQuality {
+		str.WriteString(c.FormatPrint())
+		str.WriteString("\n")
+	}
+
+	// Format low-quality categories.
+	str.WriteString(hr)
+	str.WriteString(fmt.Sprintf("│%-44s│\n", "Low Quality"))
+	str.WriteString(hr)
+	for _, c := range lowQuality {
+		str.WriteString(c.FormatPrint())
+		str.WriteString("\n")
+	}
+	str.WriteString(hr)
+
+	// Format the total.
+	var totalColor color.Color
+	total := e.Score()
+	switch {
+	case total >= 15:
+		totalColor = color.BrightGreen
+	case total >= 0:
+		totalColor = color.BrightYellow
+	default:
+		totalColor = color.BrightRed
+
+	}
+
+	max := e.Diet.MaxScore()
+	formattedTotal := strconv.FormatFloat(total, 'f', -1, 64)
+	digits := len(fmt.Sprintf("%s / %d", formattedTotal, max))
+	space := width - digits
+	format := fmt.Sprintf("%%-%ds%%s%%s%%s / %%d │\n", space)
+	str.WriteString(fmt.Sprintf(
+		format,
+		"│Total / Max: ", totalColor, formattedTotal, color.Reset, max,
+	))
+	str.WriteString(hr)
+
+	// Format the weight, delta, and body fat.
+	digits = len(fmt.Sprintf(
+		"%.2f / %.2f", e.UnitWeight(u.Units), u.UnitTargetWeight(),
+	))
+	space = width - digits
+	format = fmt.Sprintf("%%-%ds%%.2f / %%.2f │\n", space)
+	str.WriteString(fmt.Sprintf(
+		format,
+		"│Weight / Target:",
+		e.UnitWeight(u.Units),
+		u.UnitTargetWeight(),
+	))
+
+	diff := e.UnitWeight(u.Units) - u.UnitTargetWeight()
+	digits = len(fmt.Sprintf("%+.2f", diff))
+	space = width - digits
+	format = fmt.Sprintf("%%-%ds%%+.2f │\n", space)
+	str.WriteString(fmt.Sprintf(format, "│Weight Δ:", diff))
+
+	bfw := e.UnitBodyFatWeight(u.Units)
+	digits = len(fmt.Sprintf(
+		"%.2f%% (%.2f %s)",
+		e.BodyFat, bfw, u.Units.Weight(),
+	))
+	space = width - digits
+	format = fmt.Sprintf("%%-%ds%%.2f%%%% (%%.2f %%s) │\n", space)
+	str.WriteString(fmt.Sprintf(
+		format,
+		"│Body Fat:",
+		e.BodyFat, bfw, u.Units.Weight(),
+	))
+
+	bmi := stats.BMI(u.Height, e.Weight)
+	digits = len(fmt.Sprintf("%.2f", bmi))
+	space = width - digits
+	format = fmt.Sprintf("%%-%ds%%.2f │\n", space)
+	str.WriteString(fmt.Sprintf(format, "│BMI:", bmi))
+
+	str.WriteString(bottom)
+
+	// If a note is set, format it.
+	if e.Note != "" {
+		str.WriteString(fmt.Sprintf(
+			"\n%s%s%s\n", color.Italic, e.Note, color.Reset,
+		))
+	}
+
+	return str.String()
+}
diff --git a/internal/dqs/entry/units.go b/internal/dqs/entry/units.go
new file mode 100644
index 0000000..f7739c2
--- /dev/null
+++ b/internal/dqs/entry/units.go
@@ -0,0 +1,32 @@
+package entry
+
+import (
+	"code.chimeric.al/dwrz/dqs/internal/dqs/stats"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user/units"
+)
+
+func (e *Entry) UnitBodyFatWeight(system units.System) float64 {
+	bfw := stats.BodyFatWeight(e.Weight, e.BodyFat)
+
+	if system == units.Metric {
+		return bfw
+	}
+
+	return units.KilogramToPounds(bfw)
+}
+
+func (e *Entry) UnitHeight(system units.System) float64 {
+	if system == units.Metric {
+		return e.Height
+	}
+
+	return units.CentimeterToInches(e.Height)
+}
+
+func (e *Entry) UnitWeight(system units.System) float64 {
+	if system == units.Metric {
+		return e.Weight
+	}
+
+	return units.KilogramToPounds(e.Weight)
+}
diff --git a/internal/dqs/portion/portion.go b/internal/dqs/portion/portion.go
new file mode 100644
index 0000000..03a47ae
--- /dev/null
+++ b/internal/dqs/portion/portion.go
@@ -0,0 +1,70 @@
+package portion
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+)
+
+// Amount indicates how much of a single portion slot has been consumed.
+type Amount string
+
+const (
+	None Amount = ""
+	Full Amount = "full"
+	Half Amount = "half"
+)
+
+// Claimed reports whether any part of the portion slot has been consumed.
+func (a Amount) Claimed() bool {
+	switch a {
+	case Half, Full:
+		return true
+	default:
+		return false
+	}
+}
+
+// Portion represents one portion slot in a food category.
+// Points is the value of a full portion; a half portion scores half of Points.
+type Portion struct {
+	Points int    `json:"points"`
+	Amount Amount `json:"amount"`
+}
+
+// Score returns the points earned for this portion slot.
+func (p *Portion) Score() float64 {
+	switch p.Amount {
+	case Full:
+		return float64(p.Points)
+	case Half:
+		return float64(p.Points) / 2
+	case None:
+		fallthrough
+	default:
+		return float64(0)
+	}
+}
+
+// Parse parses a portion quantity string.
+// The quantity must be a non-negative multiple of 0.5.
+func Parse(quantity string) (float64, error) {
+	q, err := strconv.ParseFloat(quantity, 64)
+	if err != nil {
+		return 0, fmt.Errorf(
+			"failed to parse quantity %s: %w", quantity, err,
+		)
+	}
+	if q < 0 {
+		return 0, fmt.Errorf(
+			"negative portions (%s) are not allowed", quantity,
+		)
+	}
+	if math.Mod(q, 0.5) != 0 {
+		return 0, fmt.Errorf(
+			"quantity %f is not a full or half portion", q,
+		)
+	}
+
+	return q, nil
+}
diff --git a/internal/dqs/portion/portion_test.go b/internal/dqs/portion/portion_test.go
new file mode 100644
index 0000000..80f2a82
--- /dev/null
+++ b/internal/dqs/portion/portion_test.go
@@ -0,0 +1,84 @@
+package portion
+
+import "testing"
+
+func TestParse(t *testing.T) {
+	var tests = []struct {
+		in      string
+		want    float64
+		wantErr bool
+	}{
+		{in: "0", want: 0},
+		{in: "0.5", want: 0.5},
+		{in: "1", want: 1.0},
+		{in: "1.5", want: 1.5},
+		{in: "6", want: 6.0},
+		{in: "-0.5", wantErr: true},
+		{in: "-1", wantErr: true},
+		{in: "0.25", wantErr: true},
+		{in: "1.3", wantErr: true},
+		{in: "abc", wantErr: true},
+		{in: "", wantErr: true},
+	}
+
+	for _, tc := range tests {
+		got, err := Parse(tc.in)
+		if tc.wantErr {
+			if err == nil {
+				t.Errorf("Parse(%q) = %v, want error", tc.in, got)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("Parse(%q) unexpected error: %v", tc.in, err)
+			continue
+		}
+		if got != tc.want {
+			t.Errorf("Parse(%q) = %v, want %v", tc.in, got, tc.want)
+		}
+	}
+}
+
+func TestScoreAndClaimed(t *testing.T) {
+	var tests = []struct {
+		portion     Portion
+		wantScore   float64
+		wantClaimed bool
+	}{
+		{
+			portion:     Portion{Points: 2, Amount: None},
+			wantScore:   0,
+			wantClaimed: false,
+		},
+		{
+			portion:     Portion{Points: 2, Amount: Half},
+			wantScore:   1.0,
+			wantClaimed: true,
+		},
+		{
+			portion:     Portion{Points: 2, Amount: Full},
+			wantScore:   2.0,
+			wantClaimed: true,
+		},
+		{
+			portion:     Portion{Points: -1, Amount: Half},
+			wantScore:   -0.5,
+			wantClaimed: true,
+		},
+	}
+
+	for _, tc := range tests {
+		if got := tc.portion.Score(); got != tc.wantScore {
+			t.Errorf(
+				"%+v.Score() = %v, want %v",
+				tc.portion, got, tc.wantScore,
+			)
+		}
+		if got := tc.portion.Amount.Claimed(); got != tc.wantClaimed {
+			t.Errorf(
+				"%+v.Amount.Claimed() = %v, want %v",
+				tc.portion, got, tc.wantClaimed,
+			)
+		}
+	}
+}
diff --git a/internal/dqs/report/format.go b/internal/dqs/report/format.go
new file mode 100644
index 0000000..7ab27e0
--- /dev/null
+++ b/internal/dqs/report/format.go
@@ -0,0 +1,126 @@
+package report
+
+import (
+	"fmt"
+	"strings"
+
+	"code.chimeric.al/dwrz/dqs/pkg/color"
+)
+
+func (r *Report) Format() string {
+	var str strings.Builder
+
+	fmt.Fprintf(&str, "%sEntries%s\n", color.BrightBlack, color.Reset)
+	fmt.Fprintf(&str, "Count: %d\n", len(r.Entries))
+	if len(r.Entries) > 0 {
+		fmt.Fprintf(
+			&str,
+			"First: %s\n",
+			r.Entries[0].Date.Format("2006-01-02"),
+		)
+		fmt.Fprintf(
+			&str,
+			"Latest: %s\n",
+			r.Entries[len(r.Entries)-1].Date.Format("2006-01-02"),
+		)
+		str.WriteString("\n")
+	}
+
+	if len(r.BodyFat.Values) > 0 {
+		fmt.Fprintf(
+			&str,
+			"%sBody Fat%s\n", color.BrightBlack, color.Reset,
+		)
+		fmt.Fprintf(
+			&str,
+			"Max: %.2f on %v\n",
+			r.BodyFat.Max.Value,
+			r.BodyFat.Max.Date.Format("2006-01-02"),
+		)
+		fmt.Fprintf(
+			&str,
+			"Min: %.2f on %v\n",
+			r.BodyFat.Min.Value,
+			r.BodyFat.Min.Date.Format("2006-01-02"),
+		)
+		fmt.Fprintf(&str, "Average: %.2f\n", *r.BodyFat.Average)
+		fmt.Fprintf(&str, "Median: %.2f\n", *r.BodyFat.Median)
+		str.WriteString("\n")
+	}
+
+	if len(r.DQS.Values) > 0 {
+		fmt.Fprintf(&str, "%sDQS%s\n", color.BrightBlack, color.Reset)
+		fmt.Fprintf(
+			&str,
+			"Max: %.2f on %v\n",
+			r.DQS.Max.Value,
+			r.DQS.Max.Date.Format("2006-01-02"),
+		)
+		fmt.Fprintf(
+			&str,
+			"Min: %.2f on %v\n",
+			r.DQS.Min.Value,
+			r.DQS.Min.Date.Format("2006-01-02"),
+		)
+		fmt.Fprintf(&str, "Average: %.2f\n", *r.DQS.Average)
+		fmt.Fprintf(&str, "Median: %.2f\n", *r.DQS.Median)
+		str.WriteString("\n")
+	}
+
+	if len(r.Weight.Values) > 0 {
+		fmt.Fprintf(
+			&str, "%sWeight%s\n", color.BrightBlack, color.Reset,
+		)
+		fmt.Fprintf(
+			&str,
+			"Max: %.2f on %v\n",
+			r.Weight.Max.Value,
+			r.Weight.Max.Date.Format("2006-01-02"),
+		)
+		fmt.Fprintf(
+			&str,
+			"Min: %.2f on %v\n",
+			r.Weight.Min.Value,
+			r.Weight.Min.Date.Format("2006-01-02"),
+		)
+		fmt.Fprintf(&str, "Average: %.2f\n", *r.Weight.Average)
+		fmt.Fprintf(&str, "Median: %.2f\n", *r.Weight.Median)
+		str.WriteString("\n")
+	}
+
+	if len(r.More) > 0 || len(r.Less) > 0 {
+		fmt.Fprintf(
+			&str,
+			"%sRecommendations%s\n", color.BrightBlack, color.Reset,
+		)
+	}
+	if len(r.More) > 0 {
+		fmt.Fprintf(&str, "You should eat more:\n\n")
+		for i := 0; i < 3 && i < len(r.More); i++ {
+			rec := r.More[i]
+			fmt.Fprintf(
+				&str,
+				"%s: %d lost points (%.2f per entry).\n",
+				rec.Name,
+				rec.Points,
+				float64(rec.Points)/float64(len(r.Entries)),
+			)
+		}
+	}
+	str.WriteString("\n")
+	if len(r.Less) > 0 {
+		fmt.Fprintf(&str, "You should eat less:\n")
+		for i := 0; i < 2 && i < len(r.Less); i++ {
+			rec := r.Less[i]
+			fmt.Fprintf(
+				&str,
+				"%s: %d lost points (%.2f per entry).\n",
+				rec.Name,
+				rec.Points,
+				float64(rec.Points)/float64(len(r.Entries)),
+			)
+		}
+	}
+
+	return str.String()
+}
diff --git a/internal/dqs/report/report.go b/internal/dqs/report/report.go
new file mode 100644
index 0000000..0e171c2
--- /dev/null
+++ b/internal/dqs/report/report.go
@@ -0,0 +1,101 @@
+package report
+
+import (
+	"sort"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/stats"
+)
+
+// Recommendation identifies a category and the total points lost in it across
+// all entries in a report.
+type Recommendation struct {
+	Name   string
+	Points int
+}
+
+// Report collects summary statistics and dietary recommendations across a set
+// of entries.
+type Report struct {
+	BodyFat stats.Stats
+	DQS     stats.Stats
+	Entries []*entry.Entry
+	Weight  stats.Stats
+
+	Less []*Recommendation
+	More []*Recommendation
+}
+
+// New constructs a Report. Recommendations for "More" are high-quality
+// categories with unclaimed positive points; "Less" are categories (high or low
+// quality) with claimed negative points.
+func New(entries []*entry.Entry) *Report {
+	var (
+		bf  = []stats.DateValue{}
+		dqs = []stats.DateValue{}
+		w   = []stats.DateValue{}
+
+		unclaimed = map[string]int{}
+		negative  = map[string]int{}
+	)
+	for _, e := range entries {
+		bf = append(bf, stats.DateValue{
+			Date:  e.Date,
+			Value: e.BodyFat,
+		})
+		dqs = append(dqs, stats.DateValue{
+			Date:  e.Date,
+			Value: e.Score(),
+		})
+		w = append(w, stats.DateValue{
+			Date:  e.Date,
+			Value: e.Weight,
+		})
+
+		// Iterate through high quality categories.
+		// Collect all unclaimed positive points.
+		// Collect all claimed negative points.
+		for _, c := range e.Categories {
+			for _, p := range c.Portions {
+				if p.Points > 0 && !p.Amount.Claimed() {
+					unclaimed[c.Name] += p.Points
+				}
+				if p.Points < 0 && p.Amount.Claimed() {
+					negative[c.Name] += p.Points
+				}
+			}
+		}
+	}
+
+	// Assemble the recommendations.
+	var more = []*Recommendation{}
+	var less = []*Recommendation{}
+	for name, points := range unclaimed {
+		more = append(more, &Recommendation{
+			Name:   name,
+			Points: points,
+		})
+	}
+	for name, points := range negative {
+		less = append(less, &Recommendation{
+			Name:   name,
+			Points: points,
+		})
+	}
+	sort.Slice(more, func(i, j int) bool {
+		return more[i].Points > more[j].Points
+	})
+	sort.Slice(less, func(i, j int) bool {
+		return less[i].Points < less[j].Points
+	})
+
+	return &Report{
+		BodyFat: stats.New(bf),
+		DQS:     stats.New(dqs),
+		Weight:  stats.New(w),
+		Entries: entries,
+
+		More: more,
+		Less: less,
+	}
+}
diff --git a/internal/dqs/stats/bmi.go b/internal/dqs/stats/bmi.go
new file mode 100644
index 0000000..10a43fe
--- /dev/null
+++ b/internal/dqs/stats/bmi.go
@@ -0,0 +1,21 @@
+package stats
+
+import (
+	"math"
+)
+
+// BMI calculates Body Mass Index from height in centimeters and weight in
+// kilograms. It returns 0 if height is not positive.
+func BMI(height, weight float64) float64 {
+	if height > 0 {
+		return weight / math.Pow(height/100, 2)
+	}
+
+	return 0.0
+}
+
+// BodyFatWeight returns the mass of body fat given total weight and body fat
+// percentage (0–100). The result has the same mass unit as weight.
+func BodyFatWeight(weight, bodyFat float64) float64 {
+	return (weight * bodyFat) / 100
+}
diff --git a/internal/dqs/stats/stats.go b/internal/dqs/stats/stats.go
new file mode 100644
index 0000000..fda7ad2
--- /dev/null
+++ b/internal/dqs/stats/stats.go
@@ -0,0 +1,70 @@
+package stats
+
+import (
+	"sort"
+	"time"
+)
+
+type DateValue struct {
+	Date  time.Time
+	Value float64
+}
+
+// Stats holds summary statistics across a series of dated values.
+// Average, Max, Median, and Min are nil when Values is empty.
+type Stats struct {
+	Values  []DateValue
+	Average *float64
+	Max     *DateValue
+	Median  *float64
+	Min     *DateValue
+}
+
+// New sorts values in ascending order and computes their min, max, average,
+// and median.
+func New(values []DateValue) Stats {
+	sort.Slice(values, func(i, j int) bool {
+		return values[i].Value < values[j].Value
+	})
+
+	var (
+		max *DateValue
+		min *DateValue
+		sum float64
+	)
+	for i := range values {
+		if max == nil || values[i].Value >= max.Value {
+			max = &values[i]
+		}
+		if min == nil || values[i].Value <= min.Value {
+			min = &values[i]
+		}
+
+		sum += values[i].Value
+	}
+
+	var stats = Stats{
+		Max:    max,
+		Min:    min,
+		Values: values,
+	}
+	if len(values) > 0 {
+		avg := sum / float64(len(values))
+		stats.Average = &avg
+
+		middle := len(values) / 2
+
+		if len(values)%2 != 0 {
+			median := values[middle]
+
+			stats.Median = &median.Value
+		} else {
+			median := (values[middle-1].Value +
+				values[middle].Value) / 2
+
+			stats.Median = &median
+		}
+	}
+
+	return stats
+}
diff --git a/internal/dqs/stats/stats_test.go b/internal/dqs/stats/stats_test.go
new file mode 100644
index 0000000..895e1b0
--- /dev/null
+++ b/internal/dqs/stats/stats_test.go
@@ -0,0 +1,73 @@
+package stats
+
+import (
+	"math"
+	"testing"
+	"time"
+)
+
+func TestBMI(t *testing.T) {
+	if got := BMI(0, 70); got != 0 {
+		t.Errorf("BMI(0, 70) = %v, want 0", got)
+	}
+	if got := BMI(-10, 70); got != 0 {
+		t.Errorf("BMI(-10, 70) = %v, want 0", got)
+	}
+
+	got := BMI(175, 70)
+	want := 70 / (1.75 * 1.75)
+	if math.Abs(got-want) > 1e-9 {
+		t.Errorf("BMI(175, 70) = %v, want %v", got, want)
+	}
+}
+
+func TestBodyFatWeight(t *testing.T) {
+	got := BodyFatWeight(80, 15)
+	if got != 12 {
+		t.Errorf("BodyFatWeight(80, 15) = %v, want 12", got)
+	}
+}
+
+func TestNew(t *testing.T) {
+	empty := New(nil)
+	if empty.Average != nil || empty.Median != nil ||
+		empty.Max != nil || empty.Min != nil {
+		t.Fatalf("New(nil) = %+v, want nil pointers", empty)
+	}
+
+	d1 := time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC)
+	d2 := time.Date(2020, 1, 2, 0, 0, 0, 0, time.UTC)
+	d3 := time.Date(2020, 1, 3, 0, 0, 0, 0, time.UTC)
+	d4 := time.Date(2020, 1, 4, 0, 0, 0, 0, time.UTC)
+
+	odd := New([]DateValue{
+		{Date: d1, Value: 30},
+		{Date: d2, Value: 10},
+		{Date: d3, Value: 20},
+	})
+	if odd.Min.Value != 10 || !odd.Min.Date.Equal(d2) {
+		t.Errorf("odd.Min = %+v, want 10 on %v", odd.Min, d2)
+	}
+	if odd.Max.Value != 30 || !odd.Max.Date.Equal(d1) {
+		t.Errorf("odd.Max = %+v, want 30 on %v", odd.Max, d1)
+	}
+	if *odd.Average != 20 {
+		t.Errorf("odd.Average = %v, want 20", *odd.Average)
+	}
+	if *odd.Median != 20 {
+		t.Errorf("odd.Median = %v, want 20", *odd.Median)
+	}
+
+	even := New([]DateValue{
+		{Date: d1, Value: 40},
+		{Date: d2, Value: 10},
+		{Date: d3, Value: 20},
+		{Date: d4, Value: 30},
+	})
+	if *even.Average != 25 {
+		t.Errorf("even.Average = %v, want 25", *even.Average)
+	}
+	if *even.Median != 25 {
+		t.Errorf("even.Median = %v, want 25", *even.Median)
+	}
+}
diff --git a/internal/dqs/store/entries.go b/internal/dqs/store/entries.go
new file mode 100644
index 0000000..c281556
--- /dev/null
+++ b/internal/dqs/store/entries.go
@@ -0,0 +1,116 @@
+package store
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"sync"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+)
+
+func (s *Store) DeleteEntry(date string) error {
+	name := fmt.Sprintf("%s/%s.json", s.Dir, date)
+
+	if err := os.Remove(name); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (s *Store) GetAllEntries() ([]*entry.Entry, error) {
+	files, err := os.ReadDir(s.Dir)
+	if err != nil {
+		return nil, err
+	}
+
+	var (
+		echan       = make(chan *entry.Entry, len(files))
+		errs        = make(chan error, len(files))
+		concurrency = 24
+		sem         = make(chan struct{}, concurrency)
+		wg          sync.WaitGroup
+	)
+
+	for _, f := range files {
+		name := f.Name()
+		if f.IsDir() || filepath.Ext(name) != ".json" || name == userFile {
+			continue
+		}
+
+		wg.Add(1)
+		sem <- struct{}{}
+
+		go func(name string) {
+			defer func() {
+				<-sem
+				wg.Done()
+			}()
+
+			date := name[:len(name)-len(filepath.Ext(name))]
+
+			entry, err := s.GetEntry(date)
+			if err != nil {
+				errs <- err
+				return
+			}
+
+			echan <- entry
+		}(name)
+	}
+
+	wg.Wait()
+	close(errs)
+	close(echan)
+
+	if len(errs) > 0 {
+		return nil, <-errs
+	}
+
+	var entries = []*entry.Entry{}
+	for entry := range echan {
+		entries = append(entries, entry)
+	}
+
+	sort.Slice(entries, func(i, j int) bool {
+		return entries[i].Date.Before(entries[j].Date)
+	})
+
+	return entries, nil
+}
+
+func (s *Store) GetEntry(date string) (*entry.Entry, error) {
+	name := fmt.Sprintf("%s/%s.json", s.Dir, date)
+
+	data, err := os.ReadFile(name)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open entry file: %w", err)
+	}
+
+	var e = &entry.Entry{}
+	if err := json.Unmarshal(data, e); err != nil {
+		return nil, fmt.Errorf("failed to parse entry file: %w", err)
+	}
+
+	return e, nil
+}
+
+func (s *Store) UpdateEntry(e *entry.Entry) error {
+	data, err := json.Marshal(e)
+	if err != nil {
+		return err
+	}
+
+	name := fmt.Sprintf(
+		"%s/%s.json", s.Dir, e.Date.Format(entry.DateFormat),
+	)
+
+	if err := os.WriteFile(name, data, permissions); err != nil {
+		return err
+	}
+
+	return nil
+}
diff --git a/internal/dqs/store/store.go b/internal/dqs/store/store.go
new file mode 100644
index 0000000..73b295a
--- /dev/null
+++ b/internal/dqs/store/store.go
@@ -0,0 +1,27 @@
+package store
+
+import (
+	"fmt"
+	"os"
+)
+
+const permissions = 0700
+
+type Store struct {
+	Dir string
+}
+
+func Open(dir string) (*Store, error) {
+	var store = &Store{Dir: dir}
+
+	// Create the directory, if it doesn't exist.
+	if _, err := os.Stat(dir); os.IsNotExist(err) {
+		if err := os.MkdirAll(dir, os.ModeDir|permissions); err != nil {
+			return nil, fmt.Errorf(
+				"failed to create dqs directory: %w", err,
+			)
+		}
+	}
+
+	return store, nil
+}
diff --git a/internal/dqs/store/store_test.go b/internal/dqs/store/store_test.go
new file mode 100644
index 0000000..0f85890
--- /dev/null
+++ b/internal/dqs/store/store_test.go
@@ -0,0 +1,122 @@
+package store
+
+import (
+	"testing"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/diet"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/entry"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user/units"
+)
+
+func TestStoreUserAndEntries(t *testing.T) {
+	s, err := Open(t.TempDir())
+	if err != nil {
+		t.Fatalf("Open() error = %v", err)
+	}
+
+	u := &user.User{
+		Name:   "Test",
+		Diet:   diet.Vegetarian,
+		Units:  units.Metric,
+		Height: 175,
+		Weight: 70,
+	}
+	if err := s.UpdateUser(u); err != nil {
+		t.Fatalf("UpdateUser() error = %v", err)
+	}
+
+	gotUser, err := s.GetUser()
+	if err != nil {
+		t.Fatalf("GetUser() error = %v", err)
+	}
+	if gotUser.Name != u.Name || gotUser.Diet != u.Diet {
+		t.Errorf("GetUser() = %+v, want %+v", gotUser, u)
+	}
+
+	d1 := time.Date(2020, 1, 2, 0, 0, 0, 0, time.UTC)
+	d2 := time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC)
+
+	e1 := entry.New(d1, u)
+	c, err := e1.Category("f")
+	if err != nil {
+		t.Fatalf("Category(f) error = %v", err)
+	}
+	if err := c.Add(2); err != nil {
+		t.Fatalf("Add(2) error = %v", err)
+	}
+	if err := s.UpdateEntry(e1); err != nil {
+		t.Fatalf("UpdateEntry(e1) error = %v", err)
+	}
+
+	e2 := entry.New(d2, u)
+	if err := s.UpdateEntry(e2); err != nil {
+		t.Fatalf("UpdateEntry(e2) error = %v", err)
+	}
+
+	// Verify that mutating e1 did not mutate e2's template categories.
+	if got := e2.Score(); got != 0 {
+		t.Errorf("e2.Score() = %v, want 0", got)
+	}
+
+	entries, err := s.GetAllEntries()
+	if err != nil {
+		t.Fatalf("GetAllEntries() error = %v", err)
+	}
+	if len(entries) != 2 {
+		t.Fatalf("len(entries) = %d, want 2", len(entries))
+	}
+	if !entries[0].Date.Equal(d2) || !entries[1].Date.Equal(d1) {
+		t.Errorf(
+			"entries dates = [%v, %v], want [%v, %v]",
+			entries[0].Date, entries[1].Date, d2, d1,
+		)
+	}
+	if got := entries[1].Score(); got != 4 {
+		t.Errorf("entries[1].Score() = %v, want 4", got)
+	}
+
+	if err := s.DeleteEntry(d1.Format(entry.DateFormat)); err != nil {
+		t.Fatalf("DeleteEntry() error = %v", err)
+	}
+	entries, err = s.GetAllEntries()
+	if err != nil {
+		t.Fatalf("GetAllEntries() error = %v", err)
+	}
+	if len(entries) != 1 {
+		t.Errorf("len(entries) after delete = %d, want 1", len(entries))
+	}
+}
+
+func BenchmarkGetAllEntries(b *testing.B) {
+	b.StopTimer()
+
+	s, err := Open(b.TempDir())
+	if err != nil {
+		b.Fatalf("failed to open store: %v", err)
+	}
+
+	var start = time.Date(1900, 1, 1, 0, 0, 0, 0, time.UTC)
+	var end = time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
+
+	for t := start; t.Before(end); t = t.AddDate(0, 0, 1) {
+		if err := s.UpdateEntry(&entry.Entry{
+			Categories: diet.Vegetarian.Template(),
+			Date:       t,
+			Diet:       diet.Vegetarian,
+		}); err != nil {
+			b.Fatalf("failed to create entry: %v", err)
+		}
+	}
+
+	b.ResetTimer()
+
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		if _, err := s.GetAllEntries(); err != nil {
+			b.Fatalf("failed to get all entries: %v", err)
+		}
+	}
+	b.StopTimer()
+}
diff --git a/internal/dqs/store/user.go b/internal/dqs/store/user.go
new file mode 100644
index 0000000..645c055
--- /dev/null
+++ b/internal/dqs/store/user.go
@@ -0,0 +1,42 @@
+package store
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user"
+)
+
+const userFile = "user.json"
+
+func (s *Store) GetUser() (*user.User, error) {
+	name := fmt.Sprintf("%s/%s", s.Dir, userFile)
+
+	data, err := os.ReadFile(name)
+	if err != nil {
+		return nil, err
+	}
+
+	var u = &user.User{}
+	if err := json.Unmarshal(data, u); err != nil {
+		return nil, err
+	}
+
+	return u, nil
+}
+
+func (s *Store) UpdateUser(u *user.User) error {
+	data, err := json.Marshal(u)
+	if err != nil {
+		return err
+	}
+
+	name := fmt.Sprintf("%s/%s", s.Dir, userFile)
+
+	if err := os.WriteFile(name, data, permissions); err != nil {
+		return err
+	}
+
+	return nil
+}
diff --git a/internal/dqs/user/format.go b/internal/dqs/user/format.go
new file mode 100644
index 0000000..ddcb68f
--- /dev/null
+++ b/internal/dqs/user/format.go
@@ -0,0 +1,78 @@
+package user
+
+import (
+	"fmt"
+	"strings"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/stats"
+	"code.chimeric.al/dwrz/dqs/pkg/color"
+)
+
+func (u *User) FormatPrint() string {
+	var str strings.Builder
+
+	str.WriteString(color.BrightBlack)
+	str.WriteString("Name: ")
+	str.WriteString(color.Reset)
+	str.WriteString(u.Name)
+	str.WriteString("\n")
+
+	str.WriteString(color.BrightBlack)
+	str.WriteString("Birthday: ")
+	str.WriteString(color.Reset)
+	str.WriteString(u.Birthday.Format("2006-01-02"))
+	str.WriteString("\n")
+
+	str.WriteString(color.BrightBlack)
+	str.WriteString("Units: ")
+	str.WriteString(color.Reset)
+	str.WriteString(string(u.Units))
+	str.WriteString("\n")
+
+	str.WriteString(color.BrightBlack)
+	str.WriteString("Height: ")
+	str.WriteString(color.Reset)
+	str.WriteString(fmt.Sprintf(
+		"%.2f %s", u.UnitHeight(), u.Units.Height()),
+	)
+	str.WriteString("\n")
+
+	str.WriteString(color.BrightBlack)
+	str.WriteString("Weight: ")
+	str.WriteString(color.Reset)
+	str.WriteString(fmt.Sprintf(
+		"%.2f %s", u.UnitWeight(), u.Units.Weight()),
+	)
+	str.WriteString("\n")
+
+	str.WriteString(color.BrightBlack)
+	str.WriteString("Body Fat: ")
+	str.WriteString(color.Reset)
+	str.WriteString(fmt.Sprintf(
+		"%.2f%% (%.2f %s)",
+		u.BodyFat, u.UnitBodyFatWeight(), u.Units.Weight(),
+	))
+	str.WriteString("\n")
+
+	str.WriteString(color.BrightBlack)
+	str.WriteString("BMI: ")
+	str.WriteString(color.Reset)
+	str.WriteString(fmt.Sprintf("%.2f", stats.BMI(u.Height, u.Weight)))
+	str.WriteString("\n")
+
+	str.WriteString(color.BrightBlack)
+	str.WriteString("Diet: ")
+	str.WriteString(color.Reset)
+	str.WriteString(string(u.Diet))
+	str.WriteString("\n")
+
+	str.WriteString(color.BrightBlack)
+	str.WriteString("Target Weight: ")
+	str.WriteString(color.Reset)
+	str.WriteString(fmt.Sprintf(
+		"%.2f %s", u.UnitTargetWeight(), u.Units.Weight(),
+	))
+	str.WriteString("\n")
+
+	return str.String()
+}
diff --git a/internal/dqs/user/units.go b/internal/dqs/user/units.go
new file mode 100644
index 0000000..a0a0faa
--- /dev/null
+++ b/internal/dqs/user/units.go
@@ -0,0 +1,40 @@
+package user
+
+import (
+	"code.chimeric.al/dwrz/dqs/internal/dqs/stats"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user/units"
+)
+
+func (u *User) UnitBodyFatWeight() float64 {
+	bfw := stats.BodyFatWeight(u.Weight, u.BodyFat)
+
+	if u.Units == units.Metric {
+		return bfw
+	}
+
+	return units.KilogramToPounds(bfw)
+}
+
+func (u *User) UnitHeight() float64 {
+	if u.Units == units.Metric {
+		return u.Height
+	}
+
+	return units.CentimeterToInches(u.Height)
+}
+
+func (u *User) UnitTargetWeight() float64 {
+	if u.Units == units.Metric {
+		return u.TargetWeight
+	}
+
+	return units.KilogramToPounds(u.TargetWeight)
+}
+
+func (u *User) UnitWeight() float64 {
+	if u.Units == units.Metric {
+		return u.Weight
+	}
+
+	return units.KilogramToPounds(u.Weight)
+}
diff --git a/internal/dqs/user/units/convert.go b/internal/dqs/user/units/convert.go
new file mode 100644
index 0000000..7e79aa3
--- /dev/null
+++ b/internal/dqs/user/units/convert.go
@@ -0,0 +1,17 @@
+package units
+
+func InchesToCentimeter(inches float64) float64 {
+	return inches * 2.54
+}
+
+func CentimeterToInches(cm float64) float64 {
+	return cm / 2.54
+}
+
+func PoundsToKilogram(lbs float64) float64 {
+	return lbs * 0.45359237
+}
+
+func KilogramToPounds(kg float64) float64 {
+	return kg * 2.20462262185
+}
diff --git a/internal/dqs/user/units/units.go b/internal/dqs/user/units/units.go
new file mode 100644
index 0000000..4a608dd
--- /dev/null
+++ b/internal/dqs/user/units/units.go
@@ -0,0 +1,46 @@
+package units
+
+type System string
+
+const (
+	Default  System = "metric"
+	Imperial System = "imperial"
+	Metric   System = "metric"
+)
+
+func Valid(s System) bool {
+	switch s {
+	case Imperial, Metric:
+		return true
+	default:
+		return false
+	}
+}
+
+type Unit string
+
+const (
+	Centimeter Unit = "cm"
+	Kilogram   Unit = "kg"
+
+	Inches Unit = "in"
+	Pounds Unit = "lbs"
+)
+
+func (s System) Weight() Unit {
+	switch s {
+	case Imperial:
+		return Pounds
+	default:
+		return Kilogram
+	}
+}
+
+func (s System) Height() Unit {
+	switch s {
+	case Imperial:
+		return Inches
+	default:
+		return Centimeter
+	}
+}
diff --git a/internal/dqs/user/units/units_test.go b/internal/dqs/user/units/units_test.go
new file mode 100644
index 0000000..fe36a29
--- /dev/null
+++ b/internal/dqs/user/units/units_test.go
@@ -0,0 +1,32 @@
+package units
+
+import (
+	"math"
+	"testing"
+)
+
+func TestConversions(t *testing.T) {
+	const inches = 70.0
+	cm := InchesToCentimeter(inches)
+	if math.Abs(CentimeterToInches(cm)-inches) > 1e-9 {
+		t.Errorf("round-trip inches = %v, want %v", CentimeterToInches(cm), inches)
+	}
+
+	const lbs = 160.0
+	kg := PoundsToKilogram(lbs)
+	if math.Abs(KilogramToPounds(kg)-lbs) > 1e-6 {
+		t.Errorf("round-trip lbs = %v, want %v", KilogramToPounds(kg), lbs)
+	}
+}
+
+func TestSystem(t *testing.T) {
+	if !Valid(Metric) || !Valid(Imperial) || Valid("other") {
+		t.Errorf("unexpected Valid() results")
+	}
+	if Metric.Weight() != Kilogram || Imperial.Weight() != Pounds {
+		t.Errorf("unexpected Weight() units")
+	}
+	if Metric.Height() != Centimeter || Imperial.Height() != Inches {
+		t.Errorf("unexpected Height() units")
+	}
+}
diff --git a/internal/dqs/user/user.go b/internal/dqs/user/user.go
new file mode 100644
index 0000000..14bd463
--- /dev/null
+++ b/internal/dqs/user/user.go
@@ -0,0 +1,43 @@
+package user
+
+import (
+	"fmt"
+	"time"
+
+	"code.chimeric.al/dwrz/dqs/internal/dqs/diet"
+	"code.chimeric.al/dwrz/dqs/internal/dqs/user/units"
+)
+
+// User holds user settings and latest measurements.
+// Height, TargetWeight, and Weight are stored in metric units (cm and kg),
+// regardless of the display system selected in Units.
+type User struct {
+	Birthday     time.Time    `json:"birthday"`
+	BodyFat      float64      `json:"bodyFat"`
+	Diet         diet.Diet    `json:"diet"`
+	Height       float64      `json:"height"`
+	Name         string       `json:"name"`
+	TargetWeight float64      `json:"targetWeight"`
+	Units        units.System `json:"units"`
+	Weight       float64      `json:"weight"`
+}
+
+var DefaultUser = User{
+	Diet:  diet.Vegetarian,
+	Units: units.Metric,
+}
+
+func (u *User) SetDiet(d diet.Diet) error {
+	switch d {
+	case diet.Omnivore:
+		u.Diet = diet.Omnivore
+	case diet.Vegan:
+		u.Diet = diet.Vegan
+	case diet.Vegetarian:
+		u.Diet = diet.Vegetarian
+	default:
+		return fmt.Errorf("unrecognized diet: %s", d)
+	}
+
+	return nil
+}