A stock keeping unit is an internal identifier a retailer uses to distinguish and manage a specific sellable product or variant.
How it works in retail
A style sold in several sizes and colours usually has separate SKUs for those variants. Businesses define their own numbering or coding conventions.
A retail example
The same T-shirt in black, size medium, has a different SKU from the black, size large version.
What to keep in mind
A SKU is not the same as a standardized GTIN or the barcode symbol that carries data. Different retailers may assign different SKUs to the same product.
SKU versus style number
A style number can group a product design, while individual SKUs distinguish its sellable variants. A jacket style offered in three colours and four sizes could therefore require 12 SKUs. The exact convention is internal, but it should allow staff and systems to tell variants apart consistently.
SKU versus barcode
The SKU identifies a record within a business. A barcode is a machine-readable representation of data, and a GTIN is a standardized trade-item identifier. A product record can contain both an internal SKU and a supplier’s GTIN. Keeping those fields distinct helps avoid mismatches when receiving goods or publishing product listings.
Why consistent identifiers matter
If two different variants accidentally share a stock identifier, a sale or return can update the wrong inventory record. Clear naming conventions and controlled changes support stock counts, replenishment and reporting. An identifier should remain stable even when a customer-facing product description changes.
Examples are illustrative. Terminology and measurement conventions can vary by business and market.