A UPC is a universal, 12-digit barcode that identifies a product across all retailers and marketplaces. A SKU (Stock Keeping Unit) is your own internal code used only inside your business to track inventory. You need a UPC to list on marketplaces; you create SKUs yourself for organization.
UPC and SKU Are Not the Same Thing
One of the most common points of confusion for new sellers is the difference between a UPC and a SKU. They look similar — both are codes attached to products — but they do completely different jobs. Mixing them up leads to rejected listings and messy inventory, so it is worth getting clear on this early.
In short: a UPC is for the outside world, and a SKU is for you. The UPC tells Amazon, eBay, and every other retailer exactly which product you are selling. The SKU tells your own warehouse, spreadsheet, or software which item is which. You will almost always use both at the same time.
What Is a UPC?
A UPC (Universal Product Code) is a globally unique 12-digit number, displayed as a scannable barcode, that identifies one specific product everywhere it is sold. The same UPC works on Amazon, eBay, Walmart, and at a physical checkout counter. Once a UPC is assigned to a product, it stays with that product for life and is never reused for anything else.
Because UPCs are universal, they have to be obtained from a legitimate source so that they are unique and not already in use by another company. You buy or register a UPC once, with no recurring fee, and then assign it to a product permanently.
What Is a SKU?
A SKU (Stock Keeping Unit) is an internal code you create to track your own inventory. SKUs are not universal — two different businesses can use the exact same SKU for completely different products, and that is perfectly fine because SKUs never leave your own systems.
A good SKU is short, human-readable, and descriptive, so anyone on your team instantly understands the variant. For example, TSHIRT-RED-L immediately tells you it is a red large t-shirt. Many sellers encode category, color, size, and even supplier into their SKU structure to make picking and reporting faster.
UPC vs SKU: Side by Side
| Feature | UPC | SKU |
|---|---|---|
| Scope | Universal (global) | Internal (your business) |
| Who assigns it | Issued / purchased | You create it |
| Format | 12 digits | Any format you choose |
| Used for | Selling on marketplaces | Inventory tracking |
| Required by Amazon | Yes (most categories) | No (optional) |
| Reusable | Never | Only within your own catalog |
Do You Need Both?
Yes — most sellers use both, and they complement each other. You need a UPC to create listings on any marketplace that requires a product identifier, and you use SKUs internally to manage stock levels, pick and pack orders, and run sales reports. The UPC identifies the product to the world; the SKU identifies it to your warehouse.
When you create a listing, you typically enter the UPC in the ‘Product ID’ or ‘GTIN’ field and your SKU in the separate ‘SKU’ field. They live side by side. You can confirm a UPC is well-formed with our free UPC barcode validator before you list it.
Common Mistakes to Avoid
The biggest mistake is entering a SKU where a marketplace asks for a UPC or GTIN — it will be rejected because a SKU is not a recognized universal identifier. The second is reusing one UPC across multiple different products, which causes listings to merge and data to break. The third is making SKUs so cryptic that nobody can read them.
Keep your UPCs authentic and unique, keep your SKUs simple and consistent, and maintain a master spreadsheet that maps every product variant to both its UPC and its SKU. That single habit prevents the majority of catalog headaches.
Frequently Asked Questions
Can a SKU be the same as a UPC?
Technically you could use the UPC number as your SKU, but it is not recommended. SKUs are easier to work with when they are short and descriptive, while UPCs are long numeric strings designed for scanners.
Do I need a UPC if I already have a SKU?
Yes, if you sell on marketplaces. A SKU does not satisfy the GTIN/UPC requirement on Amazon, Walmart, or Google Shopping — those need a real UPC or EAN.
Does each variant need its own SKU and UPC?
Yes. Every sellable variant (each size, color, and style) needs both its own unique UPC and its own SKU.
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