diff --git a/backend/innercontext/api/products.py b/backend/innercontext/api/products.py
index 86b5979..25a1c82 100644
--- a/backend/innercontext/api/products.py
+++ b/backend/innercontext/api/products.py
@@ -101,6 +101,7 @@ class InventoryCreate(SQLModel):
     finished_at: Optional[date] = None
     expiry_date: Optional[date] = None
     current_weight_g: Optional[float] = None
+    last_weighed_at: Optional[date] = None
     notes: Optional[str] = None
 
 
@@ -110,6 +111,7 @@ class InventoryUpdate(SQLModel):
     finished_at: Optional[date] = None
     expiry_date: Optional[date] = None
     current_weight_g: Optional[float] = None
+    last_weighed_at: Optional[date] = None
     notes: Optional[str] = None
 
 
diff --git a/backend/innercontext/models/product.py b/backend/innercontext/models/product.py
index 42a1755..9659826 100644
--- a/backend/innercontext/models/product.py
+++ b/backend/innercontext/models/product.py
@@ -103,6 +103,8 @@ class ProductBase(SQLModel):
 
     price_tier: PriceTier | None = None
     size_ml: float | None = Field(default=None, gt=0)
+    full_weight_g: float | None = Field(default=None, gt=0)
+    empty_weight_g: float | None = Field(default=None, gt=0)
     pao_months: int | None = Field(default=None, ge=1, le=60)
 
     inci: list[str] = Field(default_factory=list)
@@ -383,6 +385,7 @@ class ProductInventory(SQLModel, table=True):
     finished_at: date | None = Field(default=None)
     expiry_date: date | None = Field(default=None)
     current_weight_g: float | None = Field(default=None, gt=0)
+    last_weighed_at: date | None = Field(default=None)
     notes: str | None = None
 
     created_at: datetime = Field(default_factory=utc_now, nullable=False)
diff --git a/frontend/src/lib/api.ts b/frontend/src/lib/api.ts
index 16e259b..5492162 100644
--- a/frontend/src/lib/api.ts
+++ b/frontend/src/lib/api.ts
@@ -69,6 +69,9 @@ export const createInventory = (
 	productId: string,
 	body: Record<string, unknown>
 ): Promise<ProductInventory> => api.post(`/products/${productId}/inventory`, body);
+export const updateInventory = (id: string, body: Record<string, unknown>): Promise<ProductInventory> =>
+	api.patch(`/inventory/${id}`, body);
+export const deleteInventory = (id: string): Promise<void> => api.del(`/inventory/${id}`);
 
 // ─── Routines ────────────────────────────────────────────────────────────────
 
diff --git a/frontend/src/lib/components/ProductForm.svelte b/frontend/src/lib/components/ProductForm.svelte
index 031b3b0..ab17872 100644
--- a/frontend/src/lib/components/ProductForm.svelte
+++ b/frontend/src/lib/components/ProductForm.svelte
@@ -668,6 +668,32 @@
 				/>
 			</div>
 
+			<div class="space-y-2">
+				<Label for="full_weight_g">Full weight (g)</Label>
+				<Input
+					id="full_weight_g"
+					name="full_weight_g"
+					type="number"
+					min="0"
+					step="0.1"
+					placeholder="e.g. 120"
+					value={product?.full_weight_g ?? ''}
+				/>
+			</div>
+
+			<div class="space-y-2">
+				<Label for="empty_weight_g">Empty weight (g)</Label>
+				<Input
+					id="empty_weight_g"
+					name="empty_weight_g"
+					type="number"
+					min="0"
+					step="0.1"
+					placeholder="e.g. 30"
+					value={product?.empty_weight_g ?? ''}
+				/>
+			</div>
+
 			<div class="space-y-2">
 				<Label for="pao_months">PAO (months)</Label>
 				<Input
diff --git a/frontend/src/lib/types.ts b/frontend/src/lib/types.ts
index bb20ca3..d1f3607 100644
--- a/frontend/src/lib/types.ts
+++ b/frontend/src/lib/types.ts
@@ -107,6 +107,7 @@ export interface ProductInventory {
 	finished_at?: string;
 	expiry_date?: string;
 	current_weight_g?: number;
+	last_weighed_at?: string;
 	notes?: string;
 	created_at: string;
 	product?: Product;
@@ -127,6 +128,8 @@ export interface Product {
 	leave_on: boolean;
 	price_tier?: PriceTier;
 	size_ml?: number;
+	full_weight_g?: number;
+	empty_weight_g?: number;
 	pao_months?: number;
 	inci: string[];
 	actives?: ActiveIngredient[];
diff --git a/frontend/src/routes/products/[id]/+page.server.ts b/frontend/src/routes/products/[id]/+page.server.ts
index 34a1cf7..1414534 100644
--- a/frontend/src/routes/products/[id]/+page.server.ts
+++ b/frontend/src/routes/products/[id]/+page.server.ts
@@ -1,4 +1,11 @@
-import { createInventory, deleteProduct, getProduct, updateProduct } from '$lib/api';
+import {
+	createInventory,
+	deleteProduct,
+	getProduct,
+	updateProduct,
+	updateInventory as apiUpdateInventory,
+	deleteInventory as apiDeleteInventory
+} from '$lib/api';
 import { error, fail, redirect } from '@sveltejs/kit';
 import type { Actions, PageServerLoad } from './$types';
 
@@ -125,6 +132,8 @@ export const actions: Actions = {
 
 		// Optional numbers
 		body.size_ml = parseOptionalFloat(form.get('size_ml') as string | null) ?? null;
+		body.full_weight_g = parseOptionalFloat(form.get('full_weight_g') as string | null) ?? null;
+		body.empty_weight_g = parseOptionalFloat(form.get('empty_weight_g') as string | null) ?? null;
 		body.pao_months = parseOptionalInt(form.get('pao_months') as string | null) ?? null;
 		body.ph_min = parseOptionalFloat(form.get('ph_min') as string | null) ?? null;
 		body.ph_max = parseOptionalFloat(form.get('ph_max') as string | null) ?? null;
@@ -199,10 +208,16 @@ export const actions: Actions = {
 		const body: Record<string, unknown> = {
 			is_opened: form.get('is_opened') === 'true'
 		};
+		const openedAt = form.get('opened_at');
+		if (openedAt) body.opened_at = openedAt;
+		const finishedAt = form.get('finished_at');
+		if (finishedAt) body.finished_at = finishedAt;
 		const expiry = form.get('expiry_date');
 		if (expiry) body.expiry_date = expiry;
 		const weight = form.get('current_weight_g');
 		if (weight) body.current_weight_g = Number(weight);
+		const lastWeighed = form.get('last_weighed_at');
+		if (lastWeighed) body.last_weighed_at = lastWeighed;
 		const notes = form.get('notes');
 		if (notes) body.notes = notes;
 		try {
@@ -211,5 +226,44 @@ export const actions: Actions = {
 		} catch (e) {
 			return fail(500, { error: (e as Error).message });
 		}
+	},
+
+	updateInventory: async ({ request }) => {
+		const form = await request.formData();
+		const inventoryId = form.get('inventory_id') as string;
+		if (!inventoryId) return fail(400, { error: 'Missing inventory_id' });
+		const body: Record<string, unknown> = {
+			is_opened: form.get('is_opened') === 'true'
+		};
+		const openedAt = form.get('opened_at');
+		body.opened_at = openedAt || null;
+		const finishedAt = form.get('finished_at');
+		body.finished_at = finishedAt || null;
+		const expiry = form.get('expiry_date');
+		body.expiry_date = expiry || null;
+		const weight = form.get('current_weight_g');
+		body.current_weight_g = weight ? Number(weight) : null;
+		const lastWeighed = form.get('last_weighed_at');
+		body.last_weighed_at = lastWeighed || null;
+		const notes = form.get('notes');
+		body.notes = notes || null;
+		try {
+			await apiUpdateInventory(inventoryId, body);
+			return { inventoryUpdated: true };
+		} catch (e) {
+			return fail(500, { error: (e as Error).message });
+		}
+	},
+
+	deleteInventory: async ({ request }) => {
+		const form = await request.formData();
+		const inventoryId = form.get('inventory_id') as string;
+		if (!inventoryId) return fail(400, { error: 'Missing inventory_id' });
+		try {
+			await apiDeleteInventory(inventoryId);
+			return { inventoryDeleted: true };
+		} catch (e) {
+			return fail(500, { error: (e as Error).message });
+		}
 	}
 };
diff --git a/frontend/src/routes/products/[id]/+page.svelte b/frontend/src/routes/products/[id]/+page.svelte
index 9379a4b..0843bc5 100644
--- a/frontend/src/routes/products/[id]/+page.svelte
+++ b/frontend/src/routes/products/[id]/+page.svelte
@@ -13,6 +13,7 @@
 	let { product } = $derived(data);
 
 	let showInventoryForm = $state(false);
+	let editingInventoryId = $state<string | null>(null);
 </script>
 
 <svelte:head><title>{product.name} — innercontext</title></svelte:head>
@@ -54,11 +55,29 @@
 		{#if form?.inventoryAdded}
 			<div class="rounded-md bg-green-50 px-4 py-3 text-sm text-green-700">Package added.</div>
 		{/if}
+		{#if form?.inventoryUpdated}
+			<div class="rounded-md bg-green-50 px-4 py-3 text-sm text-green-700">Package updated.</div>
+		{/if}
+		{#if form?.inventoryDeleted}
+			<div class="rounded-md bg-green-50 px-4 py-3 text-sm text-green-700">Package deleted.</div>
+		{/if}
 
 		{#if showInventoryForm}
 			<Card>
 				<CardContent class="pt-4">
 					<form method="POST" action="?/addInventory" use:enhance class="grid grid-cols-2 gap-4">
+						<div class="col-span-2 flex items-center gap-2">
+							<input type="checkbox" id="add_is_opened" name="is_opened" value="true" class="h-4 w-4" />
+							<Label for="add_is_opened">Already opened</Label>
+						</div>
+						<div class="space-y-1">
+							<Label for="add_opened_at">Opened date</Label>
+							<Input id="add_opened_at" name="opened_at" type="date" />
+						</div>
+						<div class="space-y-1">
+							<Label for="add_finished_at">Finished date</Label>
+							<Input id="add_finished_at" name="finished_at" type="date" />
+						</div>
 						<div class="space-y-1">
 							<Label for="expiry_date">Expiry date</Label>
 							<Input id="expiry_date" name="expiry_date" type="date" />
@@ -67,6 +86,10 @@
 							<Label for="current_weight_g">Current weight (g)</Label>
 							<Input id="current_weight_g" name="current_weight_g" type="number" min="0" />
 						</div>
+						<div class="space-y-1">
+							<Label for="add_last_weighed_at">Last weighed</Label>
+							<Input id="add_last_weighed_at" name="last_weighed_at" type="date" />
+						</div>
 						<div class="space-y-1">
 							<Label for="notes">Notes</Label>
 							<Input id="notes" name="notes" />
@@ -74,7 +97,6 @@
 						<div class="flex items-end">
 							<Button type="submit" size="sm">Add</Button>
 						</div>
-						<input type="hidden" name="is_opened" value="false" />
 					</form>
 				</CardContent>
 			</Card>
@@ -82,21 +104,141 @@
 
 		{#if product.inventory.length}
 			<div class="space-y-2">
-				{#each product.inventory as pkg}
-					<div class="flex items-center justify-between rounded-md border border-border px-4 py-3 text-sm">
-						<div class="space-x-3">
-							<Badge variant={pkg.is_opened ? 'default' : 'secondary'}>
-								{pkg.is_opened ? 'Open' : 'Sealed'}
-							</Badge>
-							{#if pkg.expiry_date}
-								<span class="text-muted-foreground">Exp: {pkg.expiry_date}</span>
-							{/if}
-							{#if pkg.current_weight_g}
-								<span class="text-muted-foreground">{pkg.current_weight_g}g remaining</span>
-							{/if}
+				{#each product.inventory as pkg (pkg.id)}
+					<div class="rounded-md border border-border text-sm">
+						<div class="flex items-center justify-between px-4 py-3">
+							<div class="flex flex-wrap items-center gap-2">
+								<Badge variant={pkg.is_opened ? 'default' : 'secondary'}>
+									{pkg.is_opened ? 'Open' : 'Sealed'}
+								</Badge>
+								{#if pkg.finished_at}
+									<Badge variant="outline">Finished</Badge>
+								{/if}
+								{#if pkg.expiry_date}
+									<span class="text-muted-foreground">Exp: {pkg.expiry_date.slice(0, 10)}</span>
+								{/if}
+								{#if pkg.opened_at}
+									<span class="text-muted-foreground">Opened: {pkg.opened_at.slice(0, 10)}</span>
+								{/if}
+								{#if pkg.finished_at}
+									<span class="text-muted-foreground">Finished: {pkg.finished_at.slice(0, 10)}</span>
+								{/if}
+								{#if pkg.current_weight_g}
+									<span class="text-muted-foreground">{pkg.current_weight_g}g remaining</span>
+								{/if}
+								{#if pkg.last_weighed_at}
+									<span class="text-muted-foreground">Weighed: {pkg.last_weighed_at.slice(0, 10)}</span>
+								{/if}
+								{#if pkg.notes}
+									<span class="text-muted-foreground">{pkg.notes}</span>
+								{/if}
+							</div>
+							<div class="flex items-center gap-1">
+								<Button
+									variant="ghost"
+									size="sm"
+									onclick={() => (editingInventoryId = editingInventoryId === pkg.id ? null : pkg.id)}
+								>
+									{editingInventoryId === pkg.id ? 'Cancel' : 'Edit'}
+								</Button>
+								<form
+									method="POST"
+									action="?/deleteInventory"
+									use:enhance
+									onsubmit={(e) => { if (!confirm('Delete this package?')) e.preventDefault(); }}
+								>
+									<input type="hidden" name="inventory_id" value={pkg.id} />
+									<Button type="submit" variant="ghost" size="sm" class="text-destructive hover:text-destructive">×</Button>
+								</form>
+							</div>
 						</div>
-						{#if pkg.notes}
-							<span class="text-muted-foreground">{pkg.notes}</span>
+
+						{#if editingInventoryId === pkg.id}
+							<div class="border-t px-4 py-3">
+								<form
+									method="POST"
+									action="?/updateInventory"
+									use:enhance={() => {
+										return async ({ result, update }) => {
+											await update();
+											if (result.type === 'success') editingInventoryId = null;
+										};
+									}}
+									class="grid grid-cols-2 gap-4"
+								>
+									<input type="hidden" name="inventory_id" value={pkg.id} />
+									<div class="col-span-2 flex items-center gap-2">
+										<input
+											type="checkbox"
+											id="edit_is_opened_{pkg.id}"
+											name="is_opened"
+											value="true"
+											checked={pkg.is_opened}
+											class="h-4 w-4"
+										/>
+										<Label for="edit_is_opened_{pkg.id}">Already opened</Label>
+									</div>
+									<div class="space-y-1">
+										<Label for="edit_opened_at_{pkg.id}">Opened date</Label>
+										<Input
+											id="edit_opened_at_{pkg.id}"
+											name="opened_at"
+											type="date"
+											value={pkg.opened_at?.slice(0, 10) ?? ''}
+										/>
+									</div>
+									<div class="space-y-1">
+										<Label for="edit_finished_at_{pkg.id}">Finished date</Label>
+										<Input
+											id="edit_finished_at_{pkg.id}"
+											name="finished_at"
+											type="date"
+											value={pkg.finished_at?.slice(0, 10) ?? ''}
+										/>
+									</div>
+									<div class="space-y-1">
+										<Label for="edit_expiry_{pkg.id}">Expiry date</Label>
+										<Input
+											id="edit_expiry_{pkg.id}"
+											name="expiry_date"
+											type="date"
+											value={pkg.expiry_date?.slice(0, 10) ?? ''}
+										/>
+									</div>
+									<div class="space-y-1">
+										<Label for="edit_weight_{pkg.id}">Current weight (g)</Label>
+										<Input
+											id="edit_weight_{pkg.id}"
+											name="current_weight_g"
+											type="number"
+											min="0"
+											value={pkg.current_weight_g ?? ''}
+										/>
+									</div>
+									<div class="space-y-1">
+										<Label for="edit_last_weighed_{pkg.id}">Last weighed</Label>
+										<Input
+											id="edit_last_weighed_{pkg.id}"
+											name="last_weighed_at"
+											type="date"
+											value={pkg.last_weighed_at?.slice(0, 10) ?? ''}
+										/>
+									</div>
+									<div class="space-y-1">
+										<Label for="edit_notes_{pkg.id}">Notes</Label>
+										<Input id="edit_notes_{pkg.id}" name="notes" value={pkg.notes ?? ''} />
+									</div>
+									<div class="flex items-end gap-2">
+										<Button type="submit" size="sm">Save</Button>
+										<Button
+											type="button"
+											variant="ghost"
+											size="sm"
+											onclick={() => (editingInventoryId = null)}
+										>Cancel</Button>
+									</div>
+								</form>
+							</div>
 						{/if}
 					</div>
 				{/each}
diff --git a/frontend/src/routes/products/new/+page.server.ts b/frontend/src/routes/products/new/+page.server.ts
index e61017e..094b0a8 100644
--- a/frontend/src/routes/products/new/+page.server.ts
+++ b/frontend/src/routes/products/new/+page.server.ts
@@ -122,6 +122,12 @@ export const actions: Actions = {
 		const size_ml = parseOptionalFloat(form.get('size_ml') as string | null);
 		if (size_ml !== undefined) payload.size_ml = size_ml;
 
+		const full_weight_g = parseOptionalFloat(form.get('full_weight_g') as string | null);
+		if (full_weight_g !== undefined) payload.full_weight_g = full_weight_g;
+
+		const empty_weight_g = parseOptionalFloat(form.get('empty_weight_g') as string | null);
+		if (empty_weight_g !== undefined) payload.empty_weight_g = empty_weight_g;
+
 		const pao_months = parseOptionalInt(form.get('pao_months') as string | null);
 		if (pao_months !== undefined) payload.pao_months = pao_months;