What is an SKU?

A shop selling a T-shirt in three colours and four sizes is not selling one product — it is selling twelve. Each of those twelve needs its own stock count, because a rail full of smalls does not help the customer who wants a large. That is what an SKU, or stock keeping unit, is for.

SKU vs barcode

• An SKU is your own code, chosen by you, usually readable: TEE-BLK-M.
• A barcode (such as an EAN or UPC) is a standard number printed on the product, often by the manufacturer, for scanning.

One product can have both: the barcode to scan, and the SKU to make sense of it.

A good SKU scheme

1. Short and readable — category, product, variant: TEE-BLK-M.
2. Same order every time — so similar products sort together.
3. No ambiguous characters — avoid O and 0, I and 1.
4. Never reused — a discontinued SKU stays retired, so old reports still make sense.

Why it matters

• Accurate stock — counted and reordered per size and colour, not per product.
• Clear reports — which sizes sell, which colours sit on the shelf.
• Easier ordering — a purchase order by SKU leaves no room for "the blue one".
• Cleaner stocktakes — see stocktake.

Common mistakes

1. One SKU for every variant. Then you never know which size to reorder.
2. Meaningless codes. A random number cannot be read at a glance on the shop floor.
3. Changing the scheme halfway. Pick one and stick to it.

In DUMA

Products can have variants — size, colour or anything else — and each variant can have its own SKU, price and stock, so you can count, sell and reorder every one separately.