What Is a UPC Code? Barcodes, GS1 and How a UPC Differs From a SKU
- Filed
- Length
- 4 min
In this page (6)
- How a UPC number is built
- UPC, EAN and GTIN: the family of numbers
- UPC vs SKU
- Does a small online shop need UPC codes?
- How to get UPC codes
- Quick answers
A UPC code, or Universal Product Code, is a 12-digit number that identifies one specific product, together with the barcode that lets a scanner read it. The same mug in the same colour and size carries the same UPC whichever shop sells it. That global, shared quality is what separates it from the stock codes a business invents for its own use.
How a UPC number is built
The standard form, called UPC-A, has three parts:
| Part | What it is | Who decides it |
|---|---|---|
| Company prefix | The first digits, identifying the brand owner | Assigned when the business licenses numbers from GS1 |
| Item reference | The following digits, identifying the individual product | Chosen by the brand owner |
| Check digit | The final digit, used to catch reading or typing errors | Calculated from the other eleven |
The prefix length varies: a company that needs only a few numbers gets a longer prefix and therefore fewer item digits, while a large manufacturer gets a shorter prefix and room for many more products.
Working out the check digit
The check digit follows a fixed rule. Take the first eleven digits, add up the ones in odd positions and multiply that sum by three, then add the digits in even positions. The check digit is whatever brings the total up to the next multiple of ten. For the illustrative number 04210005371, the odd positions add up to 6, times three makes 18, the even positions add up to 17, and the total is 35. The next multiple of ten is 40, so the check digit is 5 and the full code reads 042100053715. Scanners repeat this calculation every time and reject a code that does not add up.
UPC, EAN and GTIN: the family of numbers
- UPC-A — the 12-digit code most familiar in North America.
- UPC-E — a compressed version for very small packages, derived from a UPC-A number.
- EAN-13 — a 13-digit code widely used outside North America; modern scanners read both.
- GTIN — Global Trade Item Number, the umbrella term that covers all of the above.
When a sales channel asks for a "GTIN", a valid UPC or EAN usually satisfies it.
UPC vs SKU
| UPC | SKU | |
|---|---|---|
| Created by | The brand owner, from a licensed range | Each seller, for internal use |
| Format | 12 digits, fixed structure | Any letters and numbers the seller chooses |
| Scope | Recognised across retailers and countries | Meaningful only inside one business |
| Same product, two shops | Same UPC | Usually two different SKUs |
| Main job | Identifying the product at checkouts and in supply chains | Tracking stock, picking orders and reporting |
Most shops need both: a UPC printed on the packaging and a readable internal code in their stock system. Our guide on how to create SKU numbers covers the second half.
Does a small online shop need UPC codes?
Not always. A shop that sells only through its own website can run perfectly well without them. They become necessary, or at least very useful, when:
- physical retailers or wholesale buyers want to stock the product;
- a large sales channel asks for a GTIN on each listing;
- a warehouse or third-party logistics provider wants scannable barcodes on every unit to speed up receiving and picking;
- the business sells its own branded goods rather than reselling someone else's.
Resellers of an existing brand use the manufacturer's UPC, not a new one. Giving another company's product a fresh code makes it look like a different item and causes listing problems.
How to get UPC codes
- License numbers from GS1. GS1 is the not-for-profit standards organisation that manages these codes, with member offices in many countries. Fees depend on how many numbers a business needs and where it registers.
- Assign one number per variant. Every size, colour and pack quantity needs its own code. A six-pack and a single unit are different products.
- Record each assignment. Keep a list linking every UPC to its SKU, product name and description, and never reuse a number for a different item.
- Generate the barcode image. Many design tools can turn the number into a barcode; follow the size and quiet-zone guidance so it scans reliably.
- Test-scan printed samples on the actual packaging material before a full print run.
What about cheap codes sold online?
Some sellers offer UPCs that were licensed to another company years ago. Those numbers still point back to the original licence holder in the GS1 database, and some retailers and sales channels check that the brand on the listing matches. Buying codes this way can lead to rejected listings later, so it is worth weighing the saving against that risk. The same caution applies to anything that blurs who really makes a product; our article on where dropshippers run into legal problems explains why branding questions matter.
Quick answers
Is a UPC the same as a barcode?
Not quite. The UPC is the number; the barcode is the pattern of bars that encodes it so a scanner can read it.
Can one UPC cover several colours?
No. Each variant that a customer could order separately needs its own number.
Do UPC codes expire?
A number assigned to a product stays with it. Whether a business keeps the right to use its range depends on the terms of its GS1 licence, so read those before letting a membership lapse.