A shoe shop has 40 size-9 pairs, two colors, and three boxes mislabeled in the store room. The difference between a disappearing count and a clean one is usually the same thing: the SKU. Here is how product codes, sizes, and units work — and why getting them right at setup saves the later years.

What a SKU is for

A SKU (stock-keeping unit) is the address of one sellable thing. "Size 8 white plain tee" is a SKU; "tees" is not. When the system counts, sells, and reorders per SKU, the shelf prediction is per SKU too — which means "buy more size 8s" becomes specific instead of "the tees are low again".

Variants done right

Clothing, footwear, and packaged goods share one pattern: a base product with several sellable variants. The setup rule is simple:

  • The base is the product: the shoe model, the shirt style.
  • The variants are size, color, and pack — each carrying its own SKU, barcode (or serial number), price, and stock count.
  • The human at the till picks colour + size, not "which unknown box".

If the system sells "shoe 2 variants" as one line, quantity splits into a second action. The till experience — one choice per sale — is the first mark of a good variant model.

Units and conversions

Sell by piece, by pack, by case, by kilogram — the system must know how each unit converts so stock, margins, and reporting stay honest across them. An item that arrives by the case and sells by the piece, with a reported stock of 3.2, is the system shouting "unit math missing". Get conversions right at the item master and the counting follows.

The barcode shortcut

For fast-moving goods, the SKU behind the barcode is the count's best friend: scan a pack of 12 and the system knows it added twelve, not one. Where no official barcode exists, generate and print your own labels at setup — it will buy you hours at the month-end.

The rule that saves you

Good inventory is a choreography of five-minute setup, years of trust: SKU, variant, unit, barcode, and reorder point, decided once per product at migration. Skipping the decision early buys confusion for the lifetime of the item.

RetailOS carries SKUs, variants, units, and barcodes in the product model so the count at the shelf matches the count on the screen. To get the item master right for your categories first, start a conversation.