A UPC is a Universal Product Code — a 12-digit number, printed as a barcode, that identifies a specific product worldwide. Every retailer scanning that code sees the same product, because the number is issued centrally and belongs to one item and one manufacturer.
That universality is the whole point, and it is what separates a UPC from the internal codes a business invents for itself. Your own product code means something inside your business. A UPC means the same thing in every shop, warehouse and marketplace that reads it.
What a UPC is, and what it stands for
UPC stands for Universal Product Code. It was introduced in the United States in 1974 — the first item ever scanned at a checkout was a packet of chewing gum — and it remains the standard retail product identifier across North America.
The number is issued through GS1, the global not-for-profit organisation that maintains product identification standards. GS1 allocates each company a unique prefix, and the company assigns its own product numbers within that prefix. Because no two companies share a prefix, no two products share a code.
A UPC identifies a product, not a unit. Every identical item carries the same UPC — a thousand tins of the same soup share one code. A code that identifies an individual unit is a serial number, which is a different thing entirely.
The barcode itself is the machine-readable representation. The digits are the identifier; the bars are simply how a scanner reads them.
The 12 digits, decoded
A standard UPC-A code looks like this:
0 12345 67890 5 │ └──┬──┘ └──┬──┘ │ │ │ │ └── Check digit (1 digit) │ │ └─────── Item reference (5 digits) │ └─────────────── Company prefix (5 digits) └──────────────────── Number system (1 digit)
The number system digit (1 digit). Indicates the broad category of code. 0, 1, 6, 7 and 8 are standard retail goods. 2 is reserved for items weighed or priced in-store, such as meat and produce, where the price is embedded in the code. 3 is pharmaceuticals and health items. 4 is retailer-internal use, never seen outside one chain. 5 and 9 are coupons.
The company prefix (typically 5 digits). Identifies the manufacturer or brand owner, assigned by GS1 and unique to that company. The prefix is not always exactly five digits — GS1 issues longer prefixes to companies needing fewer product numbers and shorter prefixes to those needing more, so the split between prefix and item reference varies.
The item reference (typically 5 digits). Assigned by the company itself to each of its products. This is where a business decides that code 00123 is the 500ml bottle and 00124 is the 750ml. Every size, colour, flavour and pack quantity needs its own number.
The check digit (1 digit). A calculated digit that verifies the other eleven were read correctly. It is not chosen; it is derived arithmetically, which is why a UPC cannot simply be made up.
UPC-A vs UPC-E
UPC-A is the standard 12-digit version — the familiar rectangle on almost every retail pack. It is what you should use unless you have a specific reason not to.
UPC-E is a compressed 6-digit version for products too small to carry a full barcode. Cosmetics, confectionery, small electronics, sample sizes.
UPC-E works by suppressing zeros. A UPC-A number containing particular patterns of zeros can be shortened by removing them, and any scanner reading a UPC-E expands it back to the full 12 digits before looking it up. Nothing is lost — the underlying identifier is the same number.
The limitation is that only UPC-A numbers with the right zero patterns can be compressed. You cannot choose UPC-E for an arbitrary product; the number has to qualify. In practice this means requesting a compressible number from the start if you know a product will need a small code.
UPC vs SKU vs EAN vs GTIN vs part number
The most common source of confusion, and the distinction is simpler than it looks.
| What it is | Who assigns it | Scope | Digits | |
|---|---|---|---|---|
| UPC | Retail product identifier, North America | GS1, via a company prefix | Global and universal | 12 |
| EAN | The international equivalent of a UPC | GS1, via a company prefix | Global and universal | 13 (or 8) |
| GTIN | The umbrella standard that covers both | GS1 | Global and universal | 8, 12, 13 or 14 |
| SKU | Your own internal product code | You | Internal to your business | Any format you choose |
| Part number | A manufacturer’s own reference for a component | The manufacturer | That manufacturer’s catalogue | Any format |
| ASIN | Amazon’s internal product identifier | Amazon | Amazon only | 10 characters |
The two distinctions that matter.
First: a UPC is external and standardised; a SKU is internal and yours. The same product has one UPC worldwide and as many SKUs as there are businesses handling it. Your SKU might be TSH-BLU-M, which tells your team it is a blue medium t-shirt. The UPC is a number that tells a scanner anywhere which exact product it is looking at.
Second: UPC and EAN are both GTINs. GTIN — Global Trade Item Number — is the umbrella standard, and a UPC is simply a 12-digit GTIN whilst an EAN is a 13-digit one. This is why marketplace listing forms increasingly ask for a “GTIN” rather than a UPC: it accepts either.
A practical note on UPC and EAN together. A 12-digit UPC becomes a valid 13-digit EAN by adding a leading zero. Systems handling both usually store everything as 13 or 14 digits internally, which is why a UPC sometimes appears in your records with a zero in front that you did not add.
How the check digit works
The check digit is calculated from the other eleven, which is what lets a scanner reject a misread rather than accepting a wrong product.
The method, using the example 01234567890?:
Step 1 — add the digits in the odd positions (1st, 3rd, 5th, 7th, 9th, 11th): 0 + 2 + 4 + 6 + 8 + 0 = 20
Step 2 — multiply that by 3: 20 × 3 = 60
Step 3 — add the digits in the even positions (2nd, 4th, 6th, 8th, 10th): 1 + 3 + 5 + 7 + 9 = 25
Step 4 — add the two results: 60 + 25 = 85
Step 5 — find what takes it to the next multiple of ten. The next multiple of ten above 85 is 90. 90 − 85 = 5
The check digit is 5, making the complete code 012345678905.
Why it matters operationally. A scanner performs this calculation on every read. If the digits it decoded do not produce the printed check digit, it rejects the scan and beeps again rather than accepting a wrong product. That single mechanism is why scanning error rates are measured in millions of characters whilst manual keying errors are measured in hundreds — and it is why you cannot invent a UPC, because an arbitrary 12-digit number will almost certainly fail the check.
Do I need a UPC, and how do I get one?
You need one if you sell through retailers — nearly all require them — or if you list on marketplaces that demand a GTIN, which most now do for branded goods. You also need one if you supply distributors or wholesalers, whose systems are built around them.
You may not need one if you sell only through your own website and your own premises. Internal SKUs and your own barcodes are sufficient for a business that never trades through a third party’s system.
How to get one. UPCs are issued through GS1, which has a national organisation in most countries. The process:
- Apply to GS1 in the country where your business is based.
- Receive a company prefix, sized to how many products you need to identify. Smaller prefixes cost less and allow fewer products.
- Assign item references yourself within that prefix — one per distinct product, size, colour and pack quantity.
- Calculate or generate the check digit for each full code.
- Produce the barcode artwork to the correct dimensions and print it on your packaging.
Cost. GS1 charges an initial fee plus an annual renewal, scaled to the number of codes you need. A small business needing a handful of codes pays considerably less than a manufacturer needing thousands.
A caution about resold barcodes. Numbers are sold cheaply by third parties who acquired large prefixes years ago and resell individual codes. They generally scan, and they carry real problems: the code is registered to the original prefix holder rather than to you, some retailers and marketplaces reject them outright, and you have no control over the prefix. If you intend to sell through retail, the GS1 route is the one that will not cause difficulty later.
One code per variant. The most common and most expensive mistake is assigning one UPC across several sizes or colours. Retailers cannot distinguish them, stock figures merge, and correcting it means new codes and new packaging. Each distinct sellable item needs its own number.
Where to go deeper
- What is a SKU — the internal code a UPC is confused with.
- What is a barcode — how the printed symbol actually works.
- Types of barcodes — the other symbologies and when to use them.
- Barcode scanning for inventory — putting codes to work in a warehouse.
- What is inventory control — the accuracy scanning protects.
- What is RFID — the alternative identification technology.
The one-line takeaway
A UPC is a 12-digit Universal Product Code issued through GS1 that identifies a product consistently worldwide — a company prefix, an item reference you assign, and a calculated check digit that lets scanners reject misreads. It is external and standardised, which is exactly what your internal SKU is not.
Frequently asked questions
What does UPC stand for? Universal Product Code. It is a 12-digit number, printed as a barcode, that identifies a specific product consistently anywhere it is scanned. It was introduced in the United States in 1974 and is administered globally by GS1.
How many digits is a UPC? Twelve for the standard UPC-A format: one number system digit, a company prefix, an item reference, and a check digit. The compressed UPC-E format shows six digits and expands back to the full twelve when scanned.
What is the difference between a UPC and a SKU? A UPC is external, standardised and issued by GS1 — the same product carries the same UPC worldwide. A SKU is internal, chosen by you, and meaningful only within your own business. The same item can have one UPC and a different SKU in every business that handles it.
What is the difference between a UPC and an EAN? A UPC is the 12-digit North American format; an EAN is the 13-digit international one. Both are GTINs — Global Trade Item Numbers — and a UPC converts to a valid EAN by adding a leading zero. Systems handling both usually store everything at 13 or 14 digits.
How do I get a UPC? Apply to GS1 in your country. You receive a company prefix sized to the number of products you need to identify, assign item references yourself within it, calculate the check digit, and produce barcode artwork for your packaging. There is an initial fee and an annual renewal.
Can I make up my own UPC? No. The final digit is calculated from the other eleven, so an arbitrary number will fail the check and be rejected by scanners. More importantly the company prefix must be allocated to you, or your code will collide with another company’s product.
Should I buy a cheap barcode from a reseller? It is risky if you intend to sell through retail. Resold numbers come from prefixes registered to the original holder rather than to you, and some retailers and marketplaces reject them. For a business selling only through its own channels the distinction rarely bites; for anyone supplying third parties, the GS1 route avoids problems later.
Do I need a separate UPC for each product variant? Yes. Every distinct sellable item — each size, colour, flavour and pack quantity — needs its own code. Sharing one UPC across variants merges them in every retailer’s system, and correcting it later means new codes and reprinted packaging.
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