SKU (Stock Keeping Unit)
Your own unique code for one sellable product variation.
Definition
A SKU (stock keeping unit) is the unique code you assign to each distinct product variation you sell, so its stock, sales, and cost can be tracked separately from every other item. On Amazon the SKU is the identifier you set when you create a listing, which is different from the ASIN that Amazon assigns to the product itself.
Why your SKU scheme matters for an FBA seller
Every number that drives a restock decision lives at the SKU level: velocity, days of supply, reorder point, and per-unit profit. If your SKUs are messy, duplicated across listings, or reused when a product changes, those numbers blur together and you lose the ability to see which variation actually makes money.
A readable convention pays off for years. Something like brand-product-size-color keeps a growing catalog legible at a glance, so you are not decoding a random string every time you place an order or reconcile a shipment.
SKU vs ASIN vs FNSKU
These three identifiers are easy to confuse. The SKU is yours to define: you set the naming convention, and unlike the ASIN it is never shared with other sellers (though it does live in your Amazon account, not just your own systems). The ASIN is Amazon's identifier for the product itself, shared by every seller on the same listing. The FNSKU is the barcode Amazon uses to tie a physical unit of FBA inventory back to your account.
The practical takeaway: you control the SKU, so make it work for you. One catch if your scheme is already a mess: you can rename a seller SKU on an inactive listing, but you cannot cleanly rename it on a live FBA listing, so a clean convention is far easier to start than to retrofit.
How SKUs connect to your restock decisions
Reorder math runs per SKU, not per account. A blended account-level view hides the slow movers and overstates the winners. Clean, stable SKUs let you forecast each variation on its own real sales and lead time, which is the only way the reorder quantity reflects reality.
Related terms
See the real numbers on every SKU
Inventory Hero tracks velocity, days of supply, and profit per SKU against your live Amazon data, so each variation gets its own reorder plan instead of a blended guess.
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