UPC: Universal Product Code – What Is It?

Every product sold in a retail store or online marketplace needs a way to be identified. That’s where UPC codes come in. These unique product identifiers help businesses track inventory, process sales, and manage products across different sales channels.

If you sell products on Amazon, Walmart, or other marketplaces, you’ve probably come across UPC codes when creating product listings. But what exactly is a UPC code, how does it work, and do you need one for your online store?

In this article, we’ll explain what UPC codes are, how to read them, how they differ from SKUs and GTINs, and how to get UPC codes for your products.

Let’s get started.

UPC stands for Universal Product Code. It’s a 12-digit number, printed under a strip of black bars, that identifies a single trade item. The bars are the UPC-A barcode a scanner reads. The digits underneath are the GTIN-12, the actual identifier stored in retail and marketplace databases. In everyday use, people call the whole thing a UPC.

The code doesn’t hold a price or a product name. It works as a lookup key. Scan it at a register or in a warehouse, and the system pulls the price, description, and stock record tied to that number.

Two rules matter most for store owners:

• One code per variant: A t-shirt sold in 3 colors and 4 sizes needs 12 UPCs, because each combination is tracked as its own item.
• One code everywhere: The UPC belongs to the product, not the seller. Walmart, Amazon, and your WooCommerce store all reference the same number.

In the US, GS1 US, the not-for-profit organization that manages the numbering system, licenses UPCs.

A UPC number looks random, but each of its 12 digits has a job. Take the sample code GS1 US uses: 6 14141 99999 6.

Part	In the example	What it tells you
Company prefix	614141	The brand owner, assigned by GS1. Runs 6 to 10 digits.
Item reference	99999	The specific product variant, assigned by the brand. Runs 1 to 5 digits.
Check digit	6	A calculated digit that confirms the code was scanned or typed correctly.

The prefix and item reference always share 11 digits, so one grows at the other’s expense. A longer prefix leaves less room for products. That’s why a 10-digit GS1 prefix comes with a single-digit item reference: 0 through 9, and you’re out.

The check digit is math you can do on paper. Using the example:

1. Add the digits in odd positions (6 + 4 + 4 + 9 + 9 + 9 = 41) and multiply by 3, which gives 123.
2. Add the digits in even positions (1 + 1 + 1 + 9 + 9 = 21).
3. Add both totals (144), then subtract the last digit of that sum from 10 (10 − 4 = 6).

The result matches the 12th digit, so the code is valid. (When the sum already ends in 0, the check digit is 0.)

UPC-E squeezes certain UPCs into 6 digits by dropping zeros, and scanners expand it back to the full 12-digit number. You’ll spot it on small items like gum or lip balm.

These four codes get mixed up constantly, mostly because they overlap.

UPC

The Universal Product Code is a 12-digit number licensed through GS1 and printed as a scannable barcode. It’s the standard product identifier across US and Canadian retail, and marketplaces like Amazon and Walmart use it to match your listing to the right product. Each variant gets its own UPC, and that code stays the same no matter who sells the item.

SKU

A Stock Keeping Unit is an internal code you create yourself. It can be any length, include letters, and follow whatever logic suits your catalog, like TEE-BLU-M for a blue medium t-shirt. Two stores selling that same shirt share one UPC but almost always use different SKUs.

In WooCommerce, the SKU handles picking and reporting, while the UPC handles marketplaces and feeds.

GTIN

The Global Trade Item Number is the umbrella term for GS1 product identifiers. It comes in 8, 12, 13 and 14-digit formats, and a UPC is simply the 12-digit version, a GTIN-12. So when Google Merchant Center asks for a GTIN, your UPC already qualifies. No conversion needed.

EAN

The European Article Number is the 13-digit GTIN used across Europe and most markets outside North America. It’s essentially a UPC with one extra digit in front: add a leading zero to 614141999996, and you get 0614141999996, with the same check digit.

EAN-13s also scan at US checkouts, so a European brand doesn’t need a separate set of UPCs to sell to American customers.

Code	Digits	Who issues it	Where it’s used	Example
UPC	12	GS1 (licensed to the brand)	US and Canada retail, marketplaces	614141999996
EAN	13	GS1 (licensed to the brand)	Europe and most markets outside North America	614141999996
GTIN	8, 12, 13 or 14	GS1	Umbrella term covering UPC, EAN and case-level codes	Any of the above
SKU	Any length, letters allowed	You	Your own inventory and fulfillment	TEE-BLU-M

It depends on where you sell, not how big you are. Here’s how it plays out channel by channel.

• Your own WooCommerce store only: You don’t need UPCs. Shoppers never see them, and your SKUs handle inventory just fine. If you print your own barcode labels for packing, internal codes work.
• Google Shopping: If your products already carry a manufacturer’s GTIN, Google Merchant Center expects you to submit it. If you make your own products and never licensed codes, you can tell Google no identifier exists. That said, listings with a valid GTIN give Google a cleaner product match, which helps them show up in more searches.
• Amazon, Walmart and eBay: Plan on needing them. Amazon and Walmart ask for a GTIN on most new listings and check UPCs against GS1’s records, so free or resold codes can get flagged. Amazon does offer GTIN exemptions for some private-label and handmade products, and eBay lets unbranded items skip the identifier, but those are exceptions you apply for or qualify into.
• Wholesale and physical retail: You need them. Store registers run on scanned UPCs, and buyers won’t take products they can’t ring up.
• Third-party fulfillment: Most 3PLs scan barcodes to receive, pick and ship stock. Ask your provider first, since some accept SKU-based labels.

Selling from Europe? An EAN-13 covers every channel above, including US marketplaces.

How to Get a UPC Code

Legitimate UPCs come from one place in the US: GS1 US. The process takes three steps.

1. Count every variant you sell: Each size, color, flavor or pack size needs its own code. A t-shirt in 3 colors and 4 sizes is 12 UPCs, not one. Add a buffer for products you plan to launch in the next year or two.
2. Pick the right GS1 US option: For a handful of products, a single GS1 US GTIN costs $30 per code with no renewal fee. If you need more, a GS1 Company Prefix is the better buy: 10 codes cost $250 upfront plus $50 a year, and 100 codes cost $750 plus $150 a year. The prefix also ties every code to your brand, which marketplaces and retail buyers check.
3. Assign and download your barcodes: Log in to GS1 US Data Hub, assign a number to each product, add its details, and download the barcode images for your packaging or labels.

How many digits are in a UPC code?

A standard UPC-A has 12 digits: a company prefix, an item reference, and a check digit. The compressed UPC-E version used on small packaging shows 6 digits, but scanners expand it back to 12.

Are UPC codes the same at different stores?

Yes. The UPC belongs to the product, not the retailer, so the same item carries the same code at Walmart, Target or an independent shop. What changes from store to store is the SKU.

Where do I find the UPC code on a product?

Look for the barcode, usually on the back or bottom of the packaging. The UPC is the 12-digit number printed directly beneath the bars, with the first and last digits often set slightly apart.

Do I need a UPC to sell on Amazon?

For most new listings, yes. Amazon asks for a GTIN such as a UPC and checks it against GS1’s records. Brands selling their own private-label or handmade products can apply for a GTIN exemption instead.

Can I make my own UPC code?

You can generate a 12-digit number with a valid check digit, but it won’t be registered to your company. That’s fine for internal labels. For marketplaces, wholesale and retail, you need codes licensed from GS1.

UPC codes help businesses identify products, track inventory, and sell across different retail channels. You don’t need a UPC to run your own WooCommerce store, but you do when selling through marketplaces like Amazon and Walmart or expanding into physical retail.

The key is understanding the difference between UPCs, SKUs, and GTINs, and using the right identifier for each purpose. If your products require UPCs, getting them directly from GS1 ensures they’re properly registered and recognized by retailers and marketplaces.

Whether you’re running a small online store or expanding into multiple sales channels, accurate product identifiers help keep your inventory organized and your product listings consistent.