diff --git a/apps/api/prisma/migrations/20260819201838_ingredient_unit_catalog/migration.sql b/apps/api/prisma/migrations/20260819201838_ingredient_unit_catalog/migration.sql
new file mode 100644
index 0000000..fac5dd3
--- /dev/null
+++ b/apps/api/prisma/migrations/20260819201838_ingredient_unit_catalog/migration.sql
@@ -0,0 +1,42 @@
+-- Adds the `unit` reference catalog (key/type/to_base_factor) so recipe
+-- ingredient units are a closed, normalized set instead of free text —
+-- groundwork for a future unit-conversion feature (e.g. a shopping list
+-- summing "500g" + "0.5kg" of the same ingredient), not that feature
+-- itself. Seeded by reference-seed-data.ts's UNITS, same "SQL creates the
+-- shape, application code seeds the rows" split as Diet/Allergy/Ingredient.
+--
+-- `recipe_ingredient.unit` (free text) is replaced by `unit_id` (FK), with
+-- no backfill: a free-text value like "cas" or "grammes" can't be reliably
+-- mapped to a catalog key without a human in the loop. Acceptable as a
+-- straight breaking change here — the app has no real recipes yet
+-- (pre-launch) — rather than staging `unit_id` as nullable across a
+-- transition nothing will ever populate.
+/*
+  Warnings:
+
+  - You are about to drop the column `unit` on the `recipe_ingredient` table. All the data in the column will be lost.
+  - Added the required column `unit_id` to the `recipe_ingredient` table without a default value. This is not possible if the table is not empty.
+
+*/
+-- CreateEnum
+CREATE TYPE "UnitType" AS ENUM ('MASS', 'VOLUME', 'COUNT');
+
+-- AlterTable
+ALTER TABLE "recipe_ingredient" DROP COLUMN "unit",
+ADD COLUMN     "unit_id" INTEGER NOT NULL;
+
+-- CreateTable
+CREATE TABLE "unit" (
+    "id" SERIAL NOT NULL,
+    "key" TEXT NOT NULL,
+    "type" "UnitType" NOT NULL,
+    "to_base_factor" DECIMAL(12,4) NOT NULL DEFAULT 1,
+
+    CONSTRAINT "unit_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "unit_key_key" ON "unit"("key");
+
+-- AddForeignKey
+ALTER TABLE "recipe_ingredient" ADD CONSTRAINT "recipe_ingredient_unit_id_fkey" FOREIGN KEY ("unit_id") REFERENCES "unit"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
diff --git a/apps/api/prisma/schema.prisma b/apps/api/prisma/schema.prisma
index 57985d8..23bfef3 100644
--- a/apps/api/prisma/schema.prisma
+++ b/apps/api/prisma/schema.prisma
@@ -500,6 +500,44 @@ model IngredientAllergy {
   @@map("ingredient_allergy")
 }
 
+/// Which physical quantity a {@link Unit} measures — only units of the same
+/// type are ever mutually convertible via `toBaseFactor` (grams and
+/// kilograms both measure MASS; a "pincée" and a "gousse" are both COUNT
+/// but converting between *them* would need per-ingredient data no catalog
+/// entry alone can provide, so COUNT units just don't convert to each
+/// other, each stands alone with `toBaseFactor = 1`).
+enum UnitType {
+  MASS
+  VOLUME
+  COUNT
+}
+
+/// `key` is `@unique` — same idempotent-seed/no-duplicate reasoning as
+/// `Diet.key`. A stable English camelCase uid (e.g. `"tablespoon"`), not the
+/// display label — the label lives in `apps/web`'s
+/// `locales/fr/translation.json` under `catalog.units.<key>` (see
+/// `reference-seed-data.ts`'s `UNITS`).
+///
+/// Not in the original spec doc — `RecipeIngredient.unit` used to be free
+/// text ("g", "grammes", "G"…), which can never be reliably summed/converted
+/// (a future shopping list can't tell "g" and "grammes" are the same unit).
+/// This closes that off: `unit` is now a normalized, finite catalog.
+/// `toBaseFactor` is how many of this type's base unit (gram for MASS,
+/// milliliter for VOLUME, itself for COUNT) one of this unit equals —
+/// laying the groundwork for a future conversion feature (e.g. summing
+/// "500g" + "0.5kg" of the same ingredient into "1kg") without building
+/// that feature itself yet.
+model Unit {
+  id           Int      @id @default(autoincrement())
+  key          String   @unique
+  type         UnitType
+  toBaseFactor Decimal  @default(1) @db.Decimal(12, 4) @map("to_base_factor")
+
+  recipeIngredients RecipeIngredient[]
+
+  @@map("unit")
+}
+
 /// recipe <-> ingredients association. The spec documents this as a plain
 /// many-to-many, but a shopping list / batch-cooking calculation needs a
 /// quantity per recipe, so this join table carries quantity + unit
@@ -508,10 +546,11 @@ model RecipeIngredient {
   recipeId     Int     @map("recipe_id")
   ingredientId Int     @map("ingredient_id")
   quantity     Decimal @db.Decimal(10, 2)
-  unit         String
+  unitId       Int     @map("unit_id")
 
   recipe     Recipe     @relation(fields: [recipeId], references: [id], onDelete: Cascade)
   ingredient Ingredient @relation(fields: [ingredientId], references: [id], onDelete: Cascade)
+  unit       Unit       @relation(fields: [unitId], references: [id])
 
   @@id([recipeId, ingredientId])
   @@map("recipe_ingredient")
diff --git a/apps/api/src/db/reference-seed-data.ts b/apps/api/src/db/reference-seed-data.ts
index da8d74f..adb2998 100644
--- a/apps/api/src/db/reference-seed-data.ts
+++ b/apps/api/src/db/reference-seed-data.ts
@@ -4,6 +4,7 @@ import type {
   IngredientIcon,
   IngredientSubcategory,
   PrismaClient,
+  UnitType,
 } from "@prisma/client";
 
 // Short, optional-to-pick regime list — `UserProfile.dietId` stays
@@ -15,6 +16,33 @@ import type {
 // maintained independently, tied together only by this same uid string.
 export const DIETS = ["omnivore", "vegetarian", "vegan", "pescatarian", "glutenFree"];
 
+// Recipe ingredient units — a closed, normalized set replacing what used to
+// be free text (see `Unit`/`RecipeIngredient.unitId` in schema.prisma for
+// why). `toBaseFactor` is how many of the type's base unit (gram for MASS,
+// milliliter for VOLUME, itself for COUNT) one of this unit equals — MASS
+// and VOLUME units convert against each other within their own type, COUNT
+// units don't convert to one another at all (a "pincée" isn't a fixed
+// fraction of a "gousse"), so each just gets `1`. Same "English camelCase
+// uid, no French label" authoring as `DIETS`/`ALLERGENS` — the display
+// label lives in `apps/web`'s `locales/fr/translation.json` under
+// `catalog.units.<key>`.
+export const UNITS: Array<{ uid: string; type: UnitType; toBaseFactor: number }> = [
+  { uid: "gram", type: "MASS", toBaseFactor: 1 },
+  { uid: "kilogram", type: "MASS", toBaseFactor: 1000 },
+  { uid: "milliliter", type: "VOLUME", toBaseFactor: 1 },
+  { uid: "centiliter", type: "VOLUME", toBaseFactor: 10 },
+  { uid: "liter", type: "VOLUME", toBaseFactor: 1000 },
+  { uid: "tablespoon", type: "VOLUME", toBaseFactor: 15 },
+  { uid: "teaspoon", type: "VOLUME", toBaseFactor: 5 },
+  { uid: "piece", type: "COUNT", toBaseFactor: 1 },
+  { uid: "pinch", type: "COUNT", toBaseFactor: 1 },
+  { uid: "slice", type: "COUNT", toBaseFactor: 1 },
+  { uid: "clove", type: "COUNT", toBaseFactor: 1 },
+  { uid: "bunch", type: "COUNT", toBaseFactor: 1 },
+  { uid: "sachet", type: "COUNT", toBaseFactor: 1 },
+  { uid: "sprig", type: "COUNT", toBaseFactor: 1 },
+];
+
 // The 14 allergens EU Regulation 1169/2011 (Annex II) requires food
 // businesses to declare — a standard, defensible reference list rather than
 // an invented one. Split into ALLERGY (classic IgE-mediated immune
@@ -1086,6 +1114,17 @@ export async function seedReferenceData(prisma: PrismaClient): Promise<void> {
     await prisma.diet.upsert({ where: { key }, update: {}, create: { key } });
   }
 
+  // `update: { type, toBaseFactor }` (not `{}`) — same reasoning as
+  // `ALLERGENS`' `kind` below: a reseed must correct a unit's
+  // type/toBaseFactor if it's ever edited above, not just skip existing rows.
+  for (const { uid: key, type, toBaseFactor } of UNITS) {
+    await prisma.unit.upsert({
+      where: { key },
+      update: { type, toBaseFactor },
+      create: { key, type, toBaseFactor },
+    });
+  }
+
   // `Allergy` itself carries no `key` — it's the selectable instance of a
   // keyed `Category` (see schema.prisma) — so seeding an allergen means one
   // Category (upserted by key) plus exactly one Allergy row under it,
diff --git a/apps/api/src/modules/recipe/recipe.service.ts b/apps/api/src/modules/recipe/recipe.service.ts
index 324da54..0dfe196 100644
--- a/apps/api/src/modules/recipe/recipe.service.ts
+++ b/apps/api/src/modules/recipe/recipe.service.ts
@@ -8,6 +8,7 @@ import {
   type RecipeSummaryView,
   type RecipeTab,
   type RecipeView,
+  type UnitView,
   type UpdateRecipeInput,
 } from "@batch-cooking/shared";
 import type { Prisma } from "@prisma/client";
@@ -24,6 +25,7 @@ function recipeInclude(viewerId: number) {
             diets: { include: { diet: true } },
           },
         },
+        unit: true,
       },
     },
     steps: { orderBy: { order: "asc" } },
@@ -34,6 +36,12 @@ function recipeInclude(viewerId: number) {
 
 type RecipeWithDetails = Prisma.RecipeGetPayload<{ include: ReturnType<typeof recipeInclude> }>;
 type IngredientWithDetails = RecipeWithDetails["ingredients"][number]["ingredient"];
+type UnitWithDetails = RecipeWithDetails["ingredients"][number]["unit"];
+
+/** Shapes a Prisma `Unit` row into the public {@link UnitView} — same "Decimal → number" conversion `reference.service.ts`'s `getUnits` does. */
+function toUnitView(unit: UnitWithDetails): UnitView {
+  return { id: unit.id, key: unit.key, type: unit.type, toBaseFactor: Number(unit.toBaseFactor) };
+}
 
 /** Shapes a Prisma `Ingredient` (with its `allergies`/`diets` relations included) into the public {@link IngredientView} — same aplattening as `reference.service.ts`'s `getIngredients`. */
 function toIngredientView(ingredient: IngredientWithDetails): IngredientView {
@@ -92,7 +100,7 @@ function toRecipeView(recipe: RecipeWithDetails): RecipeView {
   const ingredients = recipe.ingredients.map((recipeIngredient) => ({
     ingredient: toIngredientView(recipeIngredient.ingredient),
     quantity: Number(recipeIngredient.quantity),
-    unit: recipeIngredient.unit,
+    unit: toUnitView(recipeIngredient.unit),
   }));
   return {
     ...toRecipeSummaryView(recipe),
@@ -293,6 +301,7 @@ export async function getRecipe(
  * later edits (see {@link updateRecipe}).
  *
  * @throws {HttpError} `404 INGREDIENT_NOT_FOUND` if any `ingredientId` doesn't match a reference ingredient.
+ * @throws {HttpError} `404 UNIT_NOT_FOUND` if any `unitId` doesn't match a reference unit.
  * @throws {HttpError} `404 DIET_NOT_FOUND` if any `dietId` doesn't match a reference diet.
  */
 export async function createRecipe(
@@ -301,6 +310,7 @@ export async function createRecipe(
   authorHouseId: number | null,
 ): Promise<RecipeView> {
   await assertIngredientsExist(input.ingredients.map((i) => i.ingredientId));
+  await assertUnitsExist(input.ingredients.map((i) => i.unitId));
   await assertDietsExist(input.dietIds);
 
   const created = await prisma.recipe.create({
@@ -316,7 +326,7 @@ export async function createRecipe(
         create: input.ingredients.map((ingredient) => ({
           ingredientId: ingredient.ingredientId,
           quantity: ingredient.quantity,
-          unit: ingredient.unit,
+          unitId: ingredient.unitId,
         })),
       },
       steps: {
@@ -343,6 +353,7 @@ export async function createRecipe(
  * @throws {HttpError} `404 RECIPE_NOT_FOUND` if `id` doesn't match any recipe visible to `viewerId`.
  * @throws {HttpError} `403 NOT_RECIPE_AUTHOR` if `viewerId` isn't this recipe's author.
  * @throws {HttpError} `404 INGREDIENT_NOT_FOUND` if any `ingredientId` doesn't match a reference ingredient.
+ * @throws {HttpError} `404 UNIT_NOT_FOUND` if any `unitId` doesn't match a reference unit.
  * @throws {HttpError} `404 DIET_NOT_FOUND` if any `dietId` doesn't match a reference diet.
  */
 export async function updateRecipe(
@@ -353,6 +364,7 @@ export async function updateRecipe(
 ): Promise<RecipeView> {
   await assertIsAuthor(id, viewerId, viewerHouseId);
   await assertIngredientsExist(input.ingredients.map((i) => i.ingredientId));
+  await assertUnitsExist(input.ingredients.map((i) => i.unitId));
   await assertDietsExist(input.dietIds);
 
   await prisma.$transaction([
@@ -371,7 +383,7 @@ export async function updateRecipe(
           create: input.ingredients.map((ingredient) => ({
             ingredientId: ingredient.ingredientId,
             quantity: ingredient.quantity,
-            unit: ingredient.unit,
+            unitId: ingredient.unitId,
           })),
         },
         steps: {
@@ -507,6 +519,20 @@ async function assertIngredientsExist(ingredientIds: number[]): Promise<void> {
   }
 }
 
+/** Throws `404 UNIT_NOT_FOUND` if any of `unitIds` doesn't match a reference `Unit` row. */
+async function assertUnitsExist(unitIds: number[]): Promise<void> {
+  const uniqueIds = [...new Set(unitIds)];
+  const found = await prisma.unit.findMany({
+    where: { id: { in: uniqueIds } },
+    select: { id: true },
+  });
+  if (found.length !== uniqueIds.length) {
+    const foundIds = new Set(found.map((unit) => unit.id));
+    const missing = uniqueIds.filter((id) => !foundIds.has(id));
+    throw new HttpError(404, ErrorCode.UNIT_NOT_FOUND, `Unit(s) not found: ${missing.join(", ")}`);
+  }
+}
+
 /** Throws `404 DIET_NOT_FOUND` if any of `dietIds` doesn't match a reference `Diet` row. */
 async function assertDietsExist(dietIds: number[]): Promise<void> {
   const uniqueIds = [...new Set(dietIds)];
diff --git a/apps/api/src/modules/reference/reference.routes.ts b/apps/api/src/modules/reference/reference.routes.ts
index f617c9e..46f3fe3 100644
--- a/apps/api/src/modules/reference/reference.routes.ts
+++ b/apps/api/src/modules/reference/reference.routes.ts
@@ -1,6 +1,6 @@
 import { wrapAsyncHandler } from "@batch-cooking/express-tools";
 import { Router } from "express";
-import { getAllergies, getDiets, getIngredients } from "./reference.service.js";
+import { getAllergies, getDiets, getIngredients, getUnits } from "./reference.service.js";
 
 /**
  * Router mounted at `/reference` in app.ts. Every route is deliberately
@@ -33,3 +33,10 @@ referenceRouter.get(
     res.status(200).json(await getIngredients());
   }),
 );
+
+referenceRouter.get(
+  "/units",
+  wrapAsyncHandler(async (_req, res) => {
+    res.status(200).json(await getUnits());
+  }),
+);
diff --git a/apps/api/src/modules/reference/reference.service.ts b/apps/api/src/modules/reference/reference.service.ts
index 749285a..3e212dd 100644
--- a/apps/api/src/modules/reference/reference.service.ts
+++ b/apps/api/src/modules/reference/reference.service.ts
@@ -1,4 +1,4 @@
-import type { AllergyView, DietView, IngredientView } from "@batch-cooking/shared";
+import type { AllergyView, DietView, IngredientView, UnitView } from "@batch-cooking/shared";
 import { prisma } from "../../db/prisma.js";
 
 /**
@@ -32,6 +32,23 @@ export async function getAllergies(): Promise<AllergyView[]> {
   }));
 }
 
+/**
+ * All reference recipe-ingredient units, ordered by key (see {@link getDiets}
+ * for why) — small, static list (see `reference-seed-data.ts`'s `UNITS`).
+ * `toBaseFactor` comes back as a Prisma `Decimal`, converted to a plain
+ * `number` here the same way `recipe.service.ts` does for
+ * `RecipeIngredient.quantity`.
+ */
+export async function getUnits(): Promise<UnitView[]> {
+  const units = await prisma.unit.findMany({ orderBy: { key: "asc" } });
+  return units.map((unit) => ({
+    id: unit.id,
+    key: unit.key,
+    type: unit.type,
+    toBaseFactor: Number(unit.toBaseFactor),
+  }));
+}
+
 /**
  * All reference ingredients, ordered by key (see {@link getDiets} for why),
  * each resolved to its allergens (see `IngredientAllergy` in schema.prisma)
diff --git a/apps/api/test-support/reset-db.ts b/apps/api/test-support/reset-db.ts
index c758f49..3d6c793 100644
--- a/apps/api/test-support/reset-db.ts
+++ b/apps/api/test-support/reset-db.ts
@@ -3,17 +3,17 @@ import { seedReferenceData } from "../src/db/reference-seed-data.js";
 
 // Single TRUNCATE ... CASCADE covers FK ordering and resets identity
 // sequences — used between tests/scenarios to start from a clean slate.
-// Re-seeds the Diet/Category/Allergy reference data right after truncating
-// it, so every test starts from the same realistic reference data the real
-// app seeds (`prisma/seed.ts`) rather than empty tables — tests exercising
-// dietId/allergyIds need real rows to reference.
+// Re-seeds the Diet/Category/Allergy/Unit reference data right after
+// truncating it, so every test starts from the same realistic reference
+// data the real app seeds (`prisma/seed.ts`) rather than empty tables —
+// tests exercising dietId/allergyIds/unitId need real rows to reference.
 export async function resetDatabase() {
   await prisma.$executeRawUnsafe(`
     TRUNCATE TABLE
       "user_profile_allergy", "user_preference", "allergy", "category",
       "planning_item", "planning",
       "recipe_ingredient", "step", "tech_step_mapping", "tech_step",
-      "recipe", "ingredients", "sources",
+      "recipe", "ingredients", "sources", "unit",
       "user_profiles", "diet", "house"
     RESTART IDENTITY CASCADE;
   `);
diff --git a/apps/api/test/recipe.test.ts b/apps/api/test/recipe.test.ts
index 3b51b25..3528c10 100644
--- a/apps/api/test/recipe.test.ts
+++ b/apps/api/test/recipe.test.ts
@@ -25,6 +25,12 @@ async function ingredientId(key: string): Promise<number> {
   return ingredient.id;
 }
 
+/** Resolves a reference unit's id by its `reference-seed-data.ts` uid (also its DB `key`) — same reasoning as {@link ingredientId}. */
+async function unitId(key: string): Promise<number> {
+  const unit = await prisma.unit.findFirstOrThrow({ where: { key } });
+  return unit.id;
+}
+
 describe("Recipes", () => {
   const app = createApp();
 
@@ -167,6 +173,7 @@ describe("Recipes", () => {
       const { agent } = await signup();
       const tomate = await ingredientId("tomato");
       const oeuf = await ingredientId("egg");
+      const piece = await unitId("piece");
       const vegetarien = await prisma.diet.findFirstOrThrow({
         where: { key: "vegetarian" },
       });
@@ -177,8 +184,8 @@ describe("Recipes", () => {
         portions: 2,
         dietIds: [vegetarien.id],
         ingredients: [
-          { ingredientId: tomate, quantity: 2, unit: "unité" },
-          { ingredientId: oeuf, quantity: 3, unit: "unité" },
+          { ingredientId: tomate, quantity: 2, unitId: piece },
+          { ingredientId: oeuf, quantity: 3, unitId: piece },
         ],
         steps: [{ description: "Battre les œufs" }, { description: "Ajouter les tomates" }],
       });
@@ -187,6 +194,7 @@ describe("Recipes", () => {
       expect(res.body.name).to.equal("Omelette provençale");
       expect(res.body.portions).to.equal(2);
       expect(res.body.ingredients).to.have.length(2);
+      expect(res.body.ingredients[0].unit.key).to.equal("piece");
       expect(
         res.body.steps.map((s: { description: string; order: number }) => s.order),
       ).to.deep.equal([0, 1]);
@@ -199,12 +207,13 @@ describe("Recipes", () => {
       const { agent } = await signup();
       const houseRes = await agent.post("/house").send({ name: "Chez moi" });
       const tomate = await ingredientId("tomato");
+      const piece = await unitId("piece");
 
       const res = await agent.post("/recipes").send({
         name: "Test",
         portions: 4,
         dietIds: [],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "unité" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Étape" }],
       });
 
@@ -216,7 +225,7 @@ describe("Recipes", () => {
         visibility: "HOUSE",
         portions: 4,
         dietIds: [],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "unité" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Étape" }],
       });
       const foyerRes = await agent.get("/recipes").query({ tab: "foyer" });
@@ -226,12 +235,13 @@ describe("Recipes", () => {
 
     it("rejects an unknown ingredientId with 404 INGREDIENT_NOT_FOUND", async () => {
       const { agent } = await signup();
+      const piece = await unitId("piece");
 
       const res = await agent.post("/recipes").send({
         name: "Test",
         portions: 4,
         dietIds: [],
-        ingredients: [{ ingredientId: 999_999, quantity: 1, unit: "g" }],
+        ingredients: [{ ingredientId: 999_999, quantity: 1, unitId: piece }],
         steps: [{ description: "Étape" }],
       });
 
@@ -239,15 +249,32 @@ describe("Recipes", () => {
       expect(res.body.code).to.equal(ErrorCode.INGREDIENT_NOT_FOUND);
     });
 
-    it("rejects an unknown dietId with 404 DIET_NOT_FOUND", async () => {
+    it("rejects an unknown unitId with 404 UNIT_NOT_FOUND", async () => {
       const { agent } = await signup();
       const tomate = await ingredientId("tomato");
 
+      const res = await agent.post("/recipes").send({
+        name: "Test",
+        portions: 4,
+        dietIds: [],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: 999_999 }],
+        steps: [{ description: "Étape" }],
+      });
+
+      expect(res.status).to.equal(404);
+      expect(res.body.code).to.equal(ErrorCode.UNIT_NOT_FOUND);
+    });
+
+    it("rejects an unknown dietId with 404 DIET_NOT_FOUND", async () => {
+      const { agent } = await signup();
+      const tomate = await ingredientId("tomato");
+      const piece = await unitId("piece");
+
       const res = await agent.post("/recipes").send({
         name: "Test",
         portions: 4,
         dietIds: [999_999],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "g" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Étape" }],
       });
 
@@ -273,10 +300,11 @@ describe("Recipes", () => {
     it("rejects a missing or non-positive portions with 400 VALIDATION_ERROR", async () => {
       const { agent } = await signup();
       const tomate = await ingredientId("tomato");
+      const piece = await unitId("piece");
       const basePayload = {
         name: "Test",
         dietIds: [],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "unité" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Étape" }],
       };
 
@@ -303,11 +331,12 @@ describe("Recipes", () => {
     it("returns the full recipe detail", async () => {
       const { agent } = await signup();
       const tomate = await ingredientId("tomato");
+      const piece = await unitId("piece");
       const created = await agent.post("/recipes").send({
         name: "Salade",
         portions: 4,
         dietIds: [],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "unité" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Couper" }],
       });
 
@@ -317,6 +346,7 @@ describe("Recipes", () => {
       expect(res.body.name).to.equal("Salade");
       expect(res.body.portions).to.equal(4);
       expect(res.body.ingredients[0].ingredient.key).to.equal("tomato");
+      expect(res.body.ingredients[0].unit.key).to.equal("piece");
       expect(res.body.isFavorite).to.equal(false);
     });
 
@@ -386,11 +416,13 @@ describe("Recipes", () => {
       const { agent } = await signup();
       const tomate = await ingredientId("tomato");
       const oignon = await ingredientId("onion");
+      const piece = await unitId("piece");
+      const gram = await unitId("gram");
       const created = await agent.post("/recipes").send({
         name: "Salade",
         portions: 4,
         dietIds: [],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "unité" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Couper" }],
       });
 
@@ -399,7 +431,7 @@ describe("Recipes", () => {
         portions: 6,
         visibility: "PUBLIC",
         dietIds: [],
-        ingredients: [{ ingredientId: oignon, quantity: 2, unit: "unité" }],
+        ingredients: [{ ingredientId: oignon, quantity: 2, unitId: gram }],
         steps: [{ description: "Émincer" }, { description: "Mélanger" }],
       });
 
@@ -409,18 +441,20 @@ describe("Recipes", () => {
       expect(res.body.visibility).to.equal("PUBLIC");
       expect(res.body.ingredients).to.have.length(1);
       expect(res.body.ingredients[0].ingredient.key).to.equal("onion");
+      expect(res.body.ingredients[0].unit.key).to.equal("gram");
       expect(res.body.steps).to.have.length(2);
     });
 
     it("returns 404 RECIPE_NOT_FOUND for an unknown id", async () => {
       const { agent } = await signup();
       const tomate = await ingredientId("tomato");
+      const piece = await unitId("piece");
 
       const res = await agent.patch("/recipes/999999").send({
         name: "Test",
         portions: 4,
         dietIds: [],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "unité" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Étape" }],
       });
 
@@ -431,11 +465,12 @@ describe("Recipes", () => {
     it("rejects an unknown dietId with 404 DIET_NOT_FOUND", async () => {
       const { agent } = await signup();
       const tomate = await ingredientId("tomato");
+      const piece = await unitId("piece");
       const created = await agent.post("/recipes").send({
         name: "Salade",
         portions: 4,
         dietIds: [],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "unité" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Couper" }],
       });
 
@@ -443,7 +478,7 @@ describe("Recipes", () => {
         name: "Salade",
         portions: 4,
         dietIds: [999_999],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "unité" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Couper" }],
       });
 
@@ -455,6 +490,7 @@ describe("Recipes", () => {
       const { agent, profileId } = await signup();
       const { agent: otherAgent } = await signup();
       const tomate = await ingredientId("tomato");
+      const piece = await unitId("piece");
       const recipe = await prisma.recipe.create({
         data: { name: "Publique", authorId: profileId, visibility: "PUBLIC", portions: 4 },
       });
@@ -463,7 +499,7 @@ describe("Recipes", () => {
         name: "Hack",
         portions: 4,
         dietIds: [],
-        ingredients: [{ ingredientId: tomate, quantity: 1, unit: "unité" }],
+        ingredients: [{ ingredientId: tomate, quantity: 1, unitId: piece }],
         steps: [{ description: "Étape" }],
       });
 
diff --git a/apps/api/test/reference.test.ts b/apps/api/test/reference.test.ts
index ce101d7..dd8bb46 100644
--- a/apps/api/test/reference.test.ts
+++ b/apps/api/test/reference.test.ts
@@ -74,4 +74,26 @@ describe("Reference data", () => {
       expect(byKey("tomato").allergens).to.deep.equal([]);
     });
   });
+
+  describe("GET /reference/units", () => {
+    it("returns the seeded units, no session required", async () => {
+      const res = await request(app).get("/reference/units");
+
+      expect(res.status).to.equal(200);
+      expect(res.body).to.have.length(14);
+      expect(res.body.map((u: { key: string }) => u.key)).to.include("gram");
+      expect(res.body[0]).to.have.keys(["id", "key", "type", "toBaseFactor"]);
+    });
+
+    it("resolves MASS/VOLUME toBaseFactor against their type's base unit, COUNT units all at 1", async () => {
+      const res = await request(app).get("/reference/units");
+
+      const byKey = (key: string) => res.body.find((u: { key: string }) => u.key === key);
+      expect(byKey("gram")).to.include({ type: "MASS", toBaseFactor: 1 });
+      expect(byKey("kilogram")).to.include({ type: "MASS", toBaseFactor: 1000 });
+      expect(byKey("liter")).to.include({ type: "VOLUME", toBaseFactor: 1000 });
+      expect(byKey("piece")).to.include({ type: "COUNT", toBaseFactor: 1 });
+      expect(byKey("pinch")).to.include({ type: "COUNT", toBaseFactor: 1 });
+    });
+  });
 });
diff --git a/apps/web/cypress/e2e/recipe-form.feature b/apps/web/cypress/e2e/recipe-form.feature
index 3d1db3c..cefaaa3 100644
--- a/apps/web/cypress/e2e/recipe-form.feature
+++ b/apps/web/cypress/e2e/recipe-form.feature
@@ -21,7 +21,7 @@ Feature: Recipe form — associating ingredients
     And I fill in the step description with "Couper les tomates."
     Then the "Enregistrer" button should not be disabled
     When I click the button "Enregistrer"
-    Then the recipe creation request should have included name "Salade de tomates", portions 4, and ingredient 1 with quantity 3 and unit "unité"
+    Then the recipe creation request should have included name "Salade de tomates", portions 4, and ingredient 1 with quantity 3 and unitId 1
     And the URL should include "/recettes/42"
 
   # Regression test for the exact bug reported: `crypto.randomUUID()` (used
@@ -64,6 +64,6 @@ Feature: Recipe form — associating ingredients
     When I fill in the last ingredient's quantity with "1" and unit "unité"
     And I click the button "Enregistrer"
     Then the recipe update request should have included these ingredients:
-      | ingredientId | quantity | unit  |
-      | 2            | 3        | unité |
-      | 1            | 1        | unité |
+      | ingredientId | quantity | unitId |
+      | 2            | 3        | 1      |
+      | 1            | 1        | 1      |
diff --git a/apps/web/cypress/e2e/recipe-form.ts b/apps/web/cypress/e2e/recipe-form.ts
index 469a726..2d22a99 100644
--- a/apps/web/cypress/e2e/recipe-form.ts
+++ b/apps/web/cypress/e2e/recipe-form.ts
@@ -33,9 +33,13 @@ const diets = [
   { id: 2, key: "vegetarian" },
 ];
 
+const pieceUnit = { id: 1, key: "piece", type: "COUNT", toBaseFactor: 1 };
+const gramUnit = { id: 2, key: "gram", type: "MASS", toBaseFactor: 1 };
+
 Given("the ingredient and diet catalog is available", () => {
   cy.intercept("GET", "**/reference/ingredients", { statusCode: 200, body: [tomato, egg, carrot] });
   cy.intercept("GET", "**/reference/diets", { statusCode: 200, body: diets });
+  cy.intercept("GET", "**/reference/units", { statusCode: 200, body: [pieceUnit, gramUnit] });
 });
 
 Given("creating the recipe will succeed and return id {int}", (id: number) => {
@@ -85,7 +89,7 @@ When(
   "I fill in the ingredient's quantity with {string} and unit {string}",
   (quantity: string, unit: string) => {
     cy.get(".ingredient-row .ingredient-row__quantity").type(quantity);
-    cy.get(".ingredient-row .ingredient-row__unit").type(unit);
+    cy.get(".ingredient-row .ingredient-row__unit").select(unit);
   },
 );
 
@@ -97,7 +101,7 @@ When(
   "I fill in the last ingredient's quantity with {string} and unit {string}",
   (quantity: string, unit: string) => {
     cy.get(".ingredient-row .ingredient-row__quantity").last().type(quantity);
-    cy.get(".ingredient-row .ingredient-row__unit").last().type(unit);
+    cy.get(".ingredient-row .ingredient-row__unit").last().select(unit);
   },
 );
 
@@ -114,14 +118,14 @@ Then("there should be {int} step editor items", (count: number) => {
 });
 
 Then(
-  "the recipe creation request should have included name {string}, portions {int}, and ingredient {int} with quantity {int} and unit {string}",
-  (name: string, portions: number, ingredientId: number, quantity: number, unit: string) => {
+  "the recipe creation request should have included name {string}, portions {int}, and ingredient {int} with quantity {int} and unitId {int}",
+  (name: string, portions: number, ingredientId: number, quantity: number, unitId: number) => {
     cy.wait("@createRecipe")
       .its("request.body")
       .should("deep.include", {
         name,
         portions,
-        ingredients: [{ ingredientId, quantity, unit }],
+        ingredients: [{ ingredientId, quantity, unitId }],
       });
   },
 );
@@ -138,7 +142,7 @@ Given("recipe 7 exists with an egg omelette", () => {
     allergens: [{ id: 1, key: "eggs", kind: "ALLERGY" }],
     diets: [],
     isFavorite: false,
-    ingredients: [{ ingredient: egg, quantity: 3, unit: "unité" }],
+    ingredients: [{ ingredient: egg, quantity: 3, unit: pieceUnit }],
     steps: [{ id: 1, description: "Battre les œufs.", picture: null, order: 0 }],
   };
   cy.intercept("GET", "**/recipes/7", { statusCode: 200, body: existingRecipe });
@@ -154,7 +158,7 @@ Then(
     const expected = dataTable.hashes().map((row) => ({
       ingredientId: Number(row.ingredientId),
       quantity: Number(row.quantity),
-      unit: row.unit,
+      unitId: Number(row.unitId),
     }));
     cy.wait("@updateRecipe").its("request.body.ingredients").should("deep.equal", expected);
   },
diff --git a/apps/web/cypress/e2e/recipes.cy.ts b/apps/web/cypress/e2e/recipes.cy.ts
index 39f233f..2bdb266 100644
--- a/apps/web/cypress/e2e/recipes.cy.ts
+++ b/apps/web/cypress/e2e/recipes.cy.ts
@@ -60,7 +60,7 @@ const omeletteDetail = {
         diets: [],
       },
       quantity: 3,
-      unit: "unité",
+      unit: { id: 1, key: "piece", type: "COUNT", toBaseFactor: 1 },
     },
   ],
   steps: [
diff --git a/apps/web/cypress/e2e/recipes.ts b/apps/web/cypress/e2e/recipes.ts
index b162bae..275eb90 100644
--- a/apps/web/cypress/e2e/recipes.ts
+++ b/apps/web/cypress/e2e/recipes.ts
@@ -30,7 +30,7 @@ const omeletteDetail = {
         diets: [],
       },
       quantity: 3,
-      unit: "unité",
+      unit: { id: 1, key: "piece", type: "COUNT", toBaseFactor: 1 },
     },
   ],
   steps: [
diff --git a/apps/web/src/api/client.ts b/apps/web/src/api/client.ts
index 6776771..374cbc1 100644
--- a/apps/web/src/api/client.ts
+++ b/apps/web/src/api/client.ts
@@ -17,6 +17,7 @@ import {
   type SafeUserProfile,
   type SignupInput,
   type ThemePreference,
+  type UnitView,
   type UpdateRecipeInput,
 } from "@batch-cooking/shared";
 
@@ -161,6 +162,11 @@ export class ApiClient {
     return this.request("/reference/ingredients");
   }
 
+  /** Reference list of recipe ingredient units (g, kg, cuillère à soupe…) — static, non-administrable (recipe form's per-ingredient unit select). Public — no session required. */
+  public getUnits(): Promise<UnitView[]> {
+    return this.request("/reference/units");
+  }
+
   /**
    * One catalog tab (favoris/perso/foyer/publique — see `RecipeTab`),
    * optionally narrowed further — `search` (name substring),
diff --git a/apps/web/src/features/recipes/IngredientRow.tsx b/apps/web/src/features/recipes/IngredientRow.tsx
index 7410f52..5fc47e1 100644
--- a/apps/web/src/features/recipes/IngredientRow.tsx
+++ b/apps/web/src/features/recipes/IngredientRow.tsx
@@ -1,4 +1,4 @@
-import type { IngredientView } from "@batch-cooking/shared";
+import type { IngredientView, UnitView } from "@batch-cooking/shared";
 import { useTranslation } from "react-i18next";
 import { AllergenBadges } from "./AllergenBadges";
 import { DietBadges } from "./DietBadges";
@@ -6,20 +6,22 @@ import { ReproducibleBadge } from "./ReproducibleBadge";
 import { IngredientTypeIcon } from "./ingredient-icons";
 import "./recipes.scss";
 
-/** One selected ingredient line in the recipe form — the ingredient itself (picked via `IngredientPicker`) plus its quantity/unit for this recipe. Quantity/unit are kept as raw strings while editing (not parsed to a number until submit) so an in-progress/invalid value doesn't fight the input. */
+/** One selected ingredient line in the recipe form — the ingredient itself (picked via `IngredientPicker`) plus its quantity/unit for this recipe. Quantity is kept as a raw string while editing (not parsed to a number until submit) so an in-progress/invalid value doesn't fight the input; `unit` picks from `unitsCatalog` (a closed reference list, see `Unit` in schema.prisma) rather than free text. */
 export function IngredientRow({
   ingredient,
   quantity,
-  unit,
+  unitId,
+  unitsCatalog,
   onQuantityChange,
   onUnitChange,
   onRemove,
 }: {
   ingredient: IngredientView;
   quantity: string;
-  unit: string;
+  unitId: number | null;
+  unitsCatalog: UnitView[];
   onQuantityChange: (quantity: string) => void;
-  onUnitChange: (unit: string) => void;
+  onUnitChange: (unitId: number) => void;
   onRemove: () => void;
 }) {
   const { t } = useTranslation();
@@ -39,14 +41,21 @@ export function IngredientRow({
         onChange={(e) => onQuantityChange(e.target.value)}
         aria-label={t("recipes.form.quantityLabel")}
       />
-      <input
-        type="text"
+      <select
         className="ingredient-row__unit"
-        value={unit}
-        onChange={(e) => onUnitChange(e.target.value)}
-        placeholder={t("recipes.form.unitPlaceholder")}
+        value={unitId ?? ""}
+        onChange={(e) => onUnitChange(Number(e.target.value))}
         aria-label={t("recipes.form.unitLabel")}
-      />
+      >
+        <option value="" disabled>
+          {t("recipes.form.unitPlaceholder")}
+        </option>
+        {unitsCatalog.map((unit) => (
+          <option key={unit.id} value={unit.id}>
+            {t(`catalog.units.${unit.key}`)}
+          </option>
+        ))}
+      </select>
       <AllergenBadges allergens={ingredient.allergens} />
       <DietBadges diets={ingredient.diets} />
       <ReproducibleBadge
diff --git a/apps/web/src/features/recipes/recipes.scss b/apps/web/src/features/recipes/recipes.scss
index b305bc1..a1dd7b3 100644
--- a/apps/web/src/features/recipes/recipes.scss
+++ b/apps/web/src/features/recipes/recipes.scss
@@ -722,8 +722,12 @@
     width: 5rem;
   }
 
+  // Wide enough for the longest catalog label ("cuillère à soupe") not to
+  // clip — was sized for the old free-text input's short values ("g",
+  // "unité"…) before unit became a <select> over the reference catalog
+  // (see IngredientRow.tsx), left too narrow for that one.
   &__unit {
-    width: 6rem;
+    width: 11rem;
   }
 
   &__remove {
diff --git a/apps/web/src/locales/fr/translation.json b/apps/web/src/locales/fr/translation.json
index d0e5b6c..6a444ac 100644
--- a/apps/web/src/locales/fr/translation.json
+++ b/apps/web/src/locales/fr/translation.json
@@ -20,6 +20,7 @@
     "RECIPE_NOT_FOUND": "Cette recette n'existe pas",
     "RECIPE_IN_USE": "Cette recette est encore utilisée dans un planning",
     "INGREDIENT_NOT_FOUND": "Un des ingrédients sélectionnés n'existe pas",
+    "UNIT_NOT_FOUND": "Une des unités sélectionnées n'existe pas",
     "INTERNAL_ERROR": "Une erreur est survenue, réessayez plus tard"
   },
   "auth": {
@@ -228,7 +229,7 @@
       },
       "quantityLabel": "Quantité",
       "unitLabel": "Unité",
-      "unitPlaceholder": "g, ml, unité…",
+      "unitPlaceholder": "Choisir une unité",
       "removeIngredient": "Retirer cet ingrédient",
       "stepDescriptionPlaceholder": "Décrivez cette étape…",
       "stepPicturePlaceholder": "Photo de l'étape (URL, optionnel)",
@@ -319,6 +320,22 @@
     }
   },
   "catalog": {
+    "units": {
+      "gram": "g",
+      "kilogram": "kg",
+      "milliliter": "ml",
+      "centiliter": "cl",
+      "liter": "l",
+      "tablespoon": "cuillère à soupe",
+      "teaspoon": "cuillère à café",
+      "piece": "unité",
+      "pinch": "pincée",
+      "slice": "tranche",
+      "clove": "gousse",
+      "bunch": "botte",
+      "sachet": "sachet",
+      "sprig": "brin"
+    },
     "diets": {
       "omnivore": "Omnivore",
       "vegetarian": "Végétarien",
diff --git a/apps/web/src/pages/RecipeFormPage.tsx b/apps/web/src/pages/RecipeFormPage.tsx
index e279d1d..b44878d 100644
--- a/apps/web/src/pages/RecipeFormPage.tsx
+++ b/apps/web/src/pages/RecipeFormPage.tsx
@@ -4,6 +4,7 @@ import {
   ErrorCode,
   type IngredientView,
   type RecipeVisibility,
+  type UnitView,
   createRecipeSchema,
 } from "@batch-cooking/shared";
 import { type FormEvent, useEffect, useState } from "react";
@@ -21,12 +22,12 @@ import { errorMessageService } from "../services/error-message.service";
 /** In display order — mirrors `RecipeVisibility` (schema.prisma/shared types). */
 const VISIBILITY_OPTIONS: RecipeVisibility[] = ["PERSONAL", "HOUSE", "PUBLIC"];
 
-/** One selected ingredient line — `key` is a client-only stable identity, same reasoning as `StepDraft`. */
+/** One selected ingredient line — `key` is a client-only stable identity, same reasoning as `StepDraft`. `unitId` is `null` until the user picks one (no default — unlike `portions`, there's no single "usually right" unit across every ingredient); `canSubmit` gates on every line having one set before allowing save. */
 interface IngredientLine {
   key: string;
   ingredient: IngredientView;
   quantity: string;
-  unit: string;
+  unitId: number | null;
 }
 
 /** Load state for the reference ingredient list (+ the existing recipe, when editing) this form needs before it can render. */
@@ -50,6 +51,7 @@ export function RecipeFormPage() {
   const [loadState, setLoadState] = useState<LoadState>("loading");
   const [ingredientsCatalog, setIngredientsCatalog] = useState<IngredientView[]>([]);
   const [dietsCatalog, setDietsCatalog] = useState<DietView[]>([]);
+  const [unitsCatalog, setUnitsCatalog] = useState<UnitView[]>([]);
 
   const [name, setName] = useState("");
   const [description, setDescription] = useState("");
@@ -74,12 +76,14 @@ export function RecipeFormPage() {
     Promise.all([
       apiClient.getIngredients(),
       apiClient.getDiets(),
+      apiClient.getUnits(),
       recipeId !== null ? apiClient.getRecipe(recipeId) : Promise.resolve(null),
     ])
-      .then(([ingredients, diets, recipe]) => {
+      .then(([ingredients, diets, units, recipe]) => {
         if (cancelled) return;
         setIngredientsCatalog(ingredients);
         setDietsCatalog(diets);
+        setUnitsCatalog(units);
         if (recipe) {
           setName(recipe.name);
           setDescription(recipe.description ?? "");
@@ -92,7 +96,7 @@ export function RecipeFormPage() {
               key: makeClientKey(),
               ingredient: line.ingredient,
               quantity: String(line.quantity),
-              unit: line.unit,
+              unitId: line.unit.id,
             })),
           );
           setSteps(
@@ -117,13 +121,13 @@ export function RecipeFormPage() {
   function addIngredient(ingredient: IngredientView) {
     setIngredientLines((lines) => [
       ...lines,
-      { key: makeClientKey(), ingredient, quantity: "", unit: "" },
+      { key: makeClientKey(), ingredient, quantity: "", unitId: null },
     ]);
   }
 
   function updateIngredientLine(
     key: string,
-    patch: Partial<Pick<IngredientLine, "quantity" | "unit">>,
+    patch: Partial<Pick<IngredientLine, "quantity" | "unitId">>,
   ) {
     setIngredientLines((lines) =>
       lines.map((line) => (line.key === key ? { ...line, ...patch } : line)),
@@ -142,7 +146,7 @@ export function RecipeFormPage() {
     Number.isInteger(Number(portions)) &&
     Number(portions) > 0 &&
     ingredientLines.length > 0 &&
-    ingredientLines.every((line) => Number(line.quantity) > 0 && line.unit.trim().length > 0) &&
+    ingredientLines.every((line) => Number(line.quantity) > 0 && line.unitId !== null) &&
     steps.length > 0 &&
     steps.every((step) => step.description.trim().length > 0);
 
@@ -160,7 +164,12 @@ export function RecipeFormPage() {
       ingredients: ingredientLines.map((line) => ({
         ingredientId: line.ingredient.id,
         quantity: Number(line.quantity),
-        unit: line.unit.trim(),
+        // `canSubmit` already requires every line to have a unit picked
+        // before the button is enabled — `?? 0` is just to satisfy the
+        // type here; if it's ever reached with no unit set, the schema's
+        // `positive()` check rejects it the same way an invalid quantity
+        // already does.
+        unitId: line.unitId ?? 0,
       })),
       steps: steps.map((step) => ({
         description: step.description.trim(),
@@ -264,9 +273,10 @@ export function RecipeFormPage() {
               key={line.key}
               ingredient={line.ingredient}
               quantity={line.quantity}
-              unit={line.unit}
+              unitId={line.unitId}
+              unitsCatalog={unitsCatalog}
               onQuantityChange={(quantity) => updateIngredientLine(line.key, { quantity })}
-              onUnitChange={(unit) => updateIngredientLine(line.key, { unit })}
+              onUnitChange={(unitId) => updateIngredientLine(line.key, { unitId })}
               onRemove={() => removeIngredientLine(line.key)}
             />
           ))}
diff --git a/packages/shared/src/errors/error-codes.ts b/packages/shared/src/errors/error-codes.ts
index 2f6f409..b421f4b 100644
--- a/packages/shared/src/errors/error-codes.ts
+++ b/packages/shared/src/errors/error-codes.ts
@@ -58,6 +58,8 @@ export enum ErrorCode {
   INGREDIENT_NOT_FOUND = 4046,
   /** `DELETE /planning/items/:id` given an id that doesn't match any planning item visible to the caller's household. */
   PLANNING_ITEM_NOT_FOUND = 4047,
+  /** A recipe payload's `unitId` doesn't match any reference `Unit` row. */
+  UNIT_NOT_FOUND = 4048,
   /** Unexpected/unhandled failure — the catch-all, always logged server-side. */
   INTERNAL_ERROR = 5000,
 }
diff --git a/packages/shared/src/schemas/recipe.ts b/packages/shared/src/schemas/recipe.ts
index f18103e..de31a28 100644
--- a/packages/shared/src/schemas/recipe.ts
+++ b/packages/shared/src/schemas/recipe.ts
@@ -13,7 +13,8 @@ import { z } from "zod";
 const recipeIngredientInputSchema = z.object({
   ingredientId: z.number().int().positive(),
   quantity: z.number().positive("La quantité doit être positive"),
-  unit: z.string().trim().min(1, "L'unité est requise").max(20),
+  /** References a reference `Unit` row (see `GET /reference/units`) — free-text units were replaced by this closed catalog, see `Unit` in schema.prisma. An unknown id is rejected service-side with `UNIT_NOT_FOUND`, same posture as `ingredientId`. */
+  unitId: z.number().int().positive(),
 });
 
 /**
diff --git a/packages/shared/src/types/recipe.ts b/packages/shared/src/types/recipe.ts
index 7d1c554..336a2b3 100644
--- a/packages/shared/src/types/recipe.ts
+++ b/packages/shared/src/types/recipe.ts
@@ -1,4 +1,4 @@
-import type { AllergyView, DietView, IngredientView } from "./reference.js";
+import type { AllergyView, DietView, IngredientView, UnitView } from "./reference.js";
 
 /**
  * Who can *read* a recipe — mirrors `RecipeVisibility` in schema.prisma.
@@ -12,13 +12,16 @@ export type RecipeVisibility = "PERSONAL" | "HOUSE" | "PUBLIC";
 /**
  * One ingredient line within a recipe, as returned in {@link RecipeView} —
  * the ingredient resolved to its full reference data (name, icon,
- * allergens), plus the quantity/unit specific to this recipe (carried by
- * `RecipeIngredient` in schema.prisma, not by `Ingredient` itself).
+ * allergens), plus the quantity specific to this recipe (carried by
+ * `RecipeIngredient` in schema.prisma, not by `Ingredient` itself). `unit`
+ * is likewise resolved to its full reference data (`Unit`) rather than a
+ * raw key — same "resolve at read time" treatment as `ingredient`, now that
+ * it's a catalog reference instead of free text (see `UnitView`).
  */
 export interface RecipeIngredientView {
   ingredient: IngredientView;
   quantity: number;
-  unit: string;
+  unit: UnitView;
 }
 
 /**
diff --git a/packages/shared/src/types/reference.ts b/packages/shared/src/types/reference.ts
index adb56ed..5af48e3 100644
--- a/packages/shared/src/types/reference.ts
+++ b/packages/shared/src/types/reference.ts
@@ -157,6 +157,36 @@ export const INGREDIENT_ICONS = [
 /** Inferred TS type for one {@link INGREDIENT_ICONS} member. */
 export type IngredientIcon = (typeof INGREDIENT_ICONS)[number];
 
+/**
+ * Which physical quantity a {@link UnitView} measures — mirrors `UnitType`
+ * in schema.prisma, declared by hand for the same reason as
+ * {@link AllergenKind}. Only units of the same type are ever mutually
+ * convertible via `toBaseFactor` — see {@link UnitView}.
+ */
+export type UnitType = "MASS" | "VOLUME" | "COUNT";
+
+/**
+ * A recipe ingredient unit, as returned by `GET /reference/units` —
+ * reference data (`Unit`, seeded via `reference-seed-data.ts`'s `UNITS`),
+ * same static/non-administrable status as {@link DietView}/
+ * {@link AllergyView}.
+ *
+ * `key` is a stable English camelCase uid (e.g. `"tablespoon"`), not a
+ * display label — resolved via `t(\`catalog.units.${key}\`)`, same as
+ * {@link DietView.key}. `toBaseFactor` is how many of `type`'s base unit
+ * (gram for MASS, milliliter for VOLUME, itself for COUNT) one of this unit
+ * equals — groundwork for a future conversion feature (e.g. a shopping list
+ * summing "500g" + "0.5kg" into "1kg"), not that feature itself: COUNT
+ * units all carry `toBaseFactor: 1` and don't convert to one another (a
+ * "pincée" isn't a fixed fraction of a "gousse").
+ */
+export interface UnitView {
+  id: number;
+  key: string;
+  type: UnitType;
+  toBaseFactor: number;
+}
+
 /**
  * A selectable ingredient, as returned by `GET /reference/ingredients` —
  * reference data (`Ingredient`, seeded via `apps/api/src/db/