SKU

What a SKU means

SKU stands for stock keeping unit and means an identifier for a sellable unit. The decisive point is in the wording: it is not the product that is labelled but the unit that sits on the shelf or in the warehouse system. A t-shirt in three colours and four sizes is twelve units and therefore twelve SKUs, although it is one product.

The SKU is an internal key. It is assigned by the retailer and only has to be unique inside their own system. Unlike an EAN it carries no information about manufacturer or product group and is not issued centrally anywhere.

How it differs from the neighbouring terms

Four identifiers get mixed up in daily work. The SKU is the internal key for the sellable unit. The article number is usually the same thing, though often kept at product level, which means variants are not separated. The GTIN is a standardised global number identifying the product worldwide. The EAN is one form of the GTIN with thirteen digits and appears as the barcode on the packaging.

For retail that gives a division of labour. The SKU organises the warehouse and connects stock, price and order inside your own system. The GTIN organises the product towards marketplaces, price comparison sites and suppliers. Anyone who has both can restructure internally without disturbing the outside.

What a workable scheme looks like

• No embedded meaning: anyone coding product group, colour and size into the number cannot change it later without breaking every legacy system.
• Fixed length: eight or ten digits with leading zeros beat variable lengths, which spreadsheets read as numbers and reformat.
• Store as text: a number such as 0012345 otherwise becomes the number 12345 in a spreadsheet and loses its leading zeros.
• Separate the variants: if colour and size do not live in the SKU, they live in a field next to it that nobody maintains.

Where numbering ranges break

The most common case arrives with a system change. A new marketplace, a new ERP or an acquisition forces numbers to be reassigned. If the SKU has travelled into external contact, in invoices or in customer orders, it can no longer be changed. That is why the rule holds that the SKU stays invisible to the outside and the GTIN takes over external communication.

Frequent questions

• Do I need one SKU per variant? Yes, otherwise the warehouse ships the wrong variant.
• May the SKU equal the article number? Yes, as long as both mean the same unit. Often they are identical.
• How long should it be? As short as possible and as long as needed. Eight to twelve digits are common.