diff --git a/db/migrate/20230602185352_create_units.rb b/db/migrate/20230602185352_create_units.rb
index 4b5f64c..af0cc04 100644
--- a/db/migrate/20230602185352_create_units.rb
+++ b/db/migrate/20230602185352_create_units.rb
@@ -5,7 +5,7 @@ class CreateUnits < ActiveRecord::Migration[7.0]
       t.string :symbol, null: false, limit: 15
       t.text :description
       t.decimal :multiplier, null: false, precision: 30, scale: 15, default: 1.0
-      t.references :base
+      t.references :base, foreign_key: {to_table: :units}
 
       t.timestamps null: false
     end
diff --git a/db/migrate/20250104194343_create_quantities.rb b/db/migrate/20250104194343_create_quantities.rb
new file mode 100644
index 0000000..1cdb7bc
--- /dev/null
+++ b/db/migrate/20250104194343_create_quantities.rb
@@ -0,0 +1,13 @@
+class CreateQuantities < ActiveRecord::Migration[7.2]
+  def change
+    create_table :quantities do |t|
+      t.references :user, foreign_key: true
+      t.integer :domain
+      t.string :name, null: false, limit: 31
+      t.text :description
+      t.references :parent, foreign_key: {to_table: :quantities}
+
+      t.timestamps null: false
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 0006b01..213db6f 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,19 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2023_06_02_185352) do
+ActiveRecord::Schema[7.2].define(version: 2025_01_04_194343) do
+  create_table "quantities", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "user_id"
+    t.integer "domain"
+    t.string "name", limit: 31, null: false
+    t.text "description"
+    t.bigint "parent_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["parent_id"], name: "index_quantities_on_parent_id"
+    t.index ["user_id"], name: "index_quantities_on_user_id"
+  end
+
   create_table "units", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "user_id"
     t.string "symbol", limit: 15, null: false
@@ -42,5 +54,8 @@ ActiveRecord::Schema[7.2].define(version: 2023_06_02_185352) do
     t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
   end
 
+  add_foreign_key "quantities", "quantities", column: "parent_id"
+  add_foreign_key "quantities", "users"
+  add_foreign_key "units", "units", column: "base_id"
   add_foreign_key "units", "users"
 end