SKU

SKU stands for Stock Keeping Unit: the unique identifier that distinguishes each different item within your inventory.

What counts as a distinct SKU

Any variation you need to count separately. A shirt in three sizes and two colors is six SKUs, not one. A product and that same product in a three-pack are two SKUs.

The practical rule: if you need to know how many units you have of that specific variant, it is a separate SKU.

What it is not

• Not the barcode. The barcode is the physical, machine-readable representation; the SKU is the logical identifier. One SKU can carry several barcodes depending on packaging.
• Not the manufacturer part number. That belongs to the supplier; the SKU is yours and reflects how you organize your inventory.

Why the SKU count matters

It is one of the two variables that determine a warehouse's complexity (the other is volume). An operation with 200 SKUs and one with 20,000 at the same piece volume need completely different layouts, picking strategies and systems.

As the SKU count grows, operator judgment stops scaling and a WMS that directs becomes necessary.