GTIN vs UPC vs SKU: What's the Difference?

Anyone who has set up a product listing has run into these three terms in the same form: GTIN, UPC, SKU. They get used loosely, sometimes interchangeably, which causes real problems when a marketplace rejects a listing or an inventory system can't reconcile stock counts. The three identifiers are not the same thing, and mixing them up is one of the most common mistakes new sellers make.

Here is what each one actually is, how they relate to each other, and which ones your business actually needs.

What Is the Difference Between a GTIN, UPC, and SKU?

A GTIN is a globally unique product identifier issued through GS1, a UPC is the North American barcode format that displays a 12-digit GTIN, and a SKU is an internal code your business creates for its own inventory tracking. The GTIN and UPC are external and standardized; the SKU is internal and yours to define however you like.

Think of it in terms of scope. A GTIN and the UPC that encodes it are recognized by every retailer, distributor, and marketplace that uses the GS1 system worldwide. A SKU only means something inside the business that created it. Two different stores selling the identical product with the identical UPC will each assign their own, completely different SKU to track it on their own shelves.

What Is a GTIN?

A GTIN, or Global Trade Item Number, is the unique number that identifies a specific product anywhere in the world, and it is what actually gets encoded into a barcode. GS1, the nonprofit standards organization that runs the system, issues GTINs in four lengths: 8, 12, 13, and 14 digits, each suited to a different kind of packaging or trade level.

A GTIN-12 is what most people know as a UPC. A GTIN-13 is the same idea encoded as an EAN-13, the standard used outside North America. A GTIN-14 (ITF-14) typically identifies a case or carton rather than a single retail unit, and a GTIN-8 is used on small packaging where space is tight. The digits themselves break down into a company prefix, an item reference number, and a check digit that verifies the code was read correctly. For the full breakdown of one of the most common formats, see our EAN-13 complete guide.

The key point is that a GTIN is not tied to any single retailer or region. Once GS1 assigns it, that number identifies that exact product, in that exact packaging, everywhere the GS1 system is used.

What Is a UPC?

A UPC, or Universal Product Code, is the linear barcode format used across North American retail, and it is one of the four physical formats a GTIN can take. When someone talks about "getting a barcode" for a product sold in a US store, they almost always mean getting a UPC-A, which is a 12-digit GTIN rendered as a scannable symbol.

You do not buy a UPC directly. What you actually license from GS1 is a GTIN, which you then generate as a UPC barcode image for your packaging. A UPC has two visible parts: a human-readable number and the black-and-white bars a scanner reads, both encoding the same 12 digits. Retailers require these because their point-of-sale systems and inventory software are all built around the GS1 numbering standard. For the format's full structure and history, read the UPC-A complete guide.

Outside North America, the equivalent format is EAN-13, which encodes a 13-digit GTIN instead of 12. Functionally they work the same way; a scanner just needs to recognize both formats to read either.

What Is a SKU?

A SKU, or Stock Keeping Unit, is an alphanumeric code a business creates on its own to track inventory internally, and it has no standardized format or external registry behind it. Where a GTIN is issued by GS1 and recognized industry-wide, a SKU is invented by whoever runs the warehouse or the point-of-sale system, and it only means something within that one company.

A single product with several variants, such as a shirt in three sizes and four colors, might get one GTIN per size-color combination for barcoding purposes, but a business could structure its SKUs differently, grouping or splitting them however its own reporting needs require. Two retailers selling the exact same product with the exact same UPC will still assign that product two entirely different SKUs, because each company's SKU system reflects its own warehouse layout, category structure, or reordering process rather than the product itself.

Because SKUs are internal, there is no lookup service for them the way there is for GTINs. If you need to match a SKU to a real-world product, that only works inside the system that created it.

Is a GTIN the Same as a Barcode Number?

Not quite; a GTIN is the identifying number itself, while a UPC or EAN barcode is the printed symbol that makes that number machine-readable. When a business "buys a barcode" from GS1, what it is actually licensing is a GTIN, a number that only becomes a barcode once it is rendered into the bars-and-spaces graphic that goes on packaging.

This distinction matters because the same GTIN can be represented in more than one barcode symbology depending on where the product is sold, most commonly as a UPC-A in North America and an EAN-13 elsewhere, both of which display slightly different digit counts for what is fundamentally the same underlying number. If you are setting up barcode graphics after registering with GS1, our guide to getting a barcode for your product walks through that step, including how pricing works if you have not registered yet, covered in our GS1 barcode cost guide.

Do I Need a GTIN and a SKU?

Most sellers need both, because they solve different problems. A GTIN, as a UPC or EAN barcode, is generally required if you sell through retail stores or marketplaces such as Amazon, which validate submitted GTINs against GS1's own registry and can suspend listings that fail that check. A SKU is something you should set up regardless, purely for your own inventory management.

Skipping the GTIN is only realistic if you sell exclusively direct-to-consumer through your own website or in-person, with no retail or marketplace distribution that requires a scannable, industry-standard code. Skipping the SKU is rarely a good idea even then, because without some internal identifier, tracking stock levels, reordering points, and sales by variant becomes much harder as your catalog grows past a handful of items.

How Do I Find a Product's GTIN?

The fastest way is to look at the numbers printed directly beneath the barcode on the product's packaging; that string of digits is the GTIN. If the barcode is a UPC-A, you are looking at a 12-digit GTIN; if it is an EAN-13, it is a 13-digit GTIN, and either can be typed or scanned to retrieve the same underlying identifier.

If you do not have the physical item in hand, GS1 offers a free lookup tool called Verified by GS1 that lets you search by GTIN, company name, or other identifiers, with a limit of 30 free queries per day for casual use. Businesses that need higher volume can use GS1's paid data services instead. You can also scan the barcode directly with a tool like barcodescanner.online to read the encoded number instantly rather than typing it by hand.

Sources

• Verified by GS1 - GS1's official lookup service for verifying GTINs, UPCs, EANs, and other GS1 identifiers.
• GS1 GTIN Management - GS1's standards documentation on how GTINs are structured, assigned, and managed.
• Shopify: Using SKUs to Manage Your Inventory - guidance on how SKUs function as internal inventory identifiers distinct from barcodes.