A “Stock Keeping Unit” or SKU is an ID number specific to one product variant, used internally by stores to keep track of inventory and sales. (Not to be confused with your product’s Barcode, ISBN, or UPC.)

SKUs are proprietary to your store, and you can use whatever format you want, however, it’s best to have some rhyme or reason to them. SKUs often, but not always, contain model numbers and variant codes (as opposed to a sequential string of numbers) so that they are easy to reference. For example, a tire with a model number of 476580 and a size of 34″, may have a SKU of 476580 -34.

One other thing to note is that your SKUs could be completely different than the SKUs of your vendor. You can keep their same structure, or create your own. It totally depends on the individual system for each store.

Here’s another example of SKUs in action. If a t-shirt design came in 2 colors (Black/White), 4 sizes (Small/Medium/Large/X-Large) and 2 styles (Mens/Womens), there would be a total of 16 SKUs, one for each of the following variants:

  1. Mens White Small (SKU: cat003MWS)
  2. Mens White Medium (SKU: cat003MWM)
  3. Mens White Large (SKU: cat003MWL)
  4. Mens White X-Large (SKU: cat003MWXL)
  5. Mens Black Small (SKU: cat0030MBS)
  6. Mens Black Medium (SKU: cat003MBM)
  7. Mens Black Large (SKU: cat003MBL)
  8. Mens Black X-Large (SKU: cat003MBXL)
  9. Womens White Small (SKU: cat003WWS)
  10. Womens White Medium (SKU: cat003WWM)
  11. Womens White Large (SKU: cat003WWL)
  12. Womens White X-Large (SKU: cat003MWXL)
  13. Womens Black Small (SKU: cat003WBS)
  14. Womens Black Medium (SKU: cat003WBM)
  15. Womens Black Large (SKU: cat003WBL)
  16. Womens Black X-Large (SKU: cat003WBXL)

Shopify and Lemonstand both let you have unlimited SKUs because they are tied to the number of products and product variants, which are also both unlimited.