Product Barcodes 101
Understanding the relationship between UPC (GTIN-12) and EAN (GTIN-13), and how to convert between them.
UPC (GTIN-12)
12 Digits. Primarily used in the United States & Canada. This is the standard format for North American retail.
EAN (GTIN-13)
13 Digits. Used globally (Europe, Asia, Australia). Contains a country code, but compatible with UPCs.
Convert UPC ↔ EAN
A UPC is simply an EAN with a leading zero. Use this tool to format your code for different marketplaces.
Barcode Formats Compared
| Format | Characters | Primary Use |
|---|---|---|
| UPC-A (GTIN-12) | 12 Digits | Retail Point-of-Sale (North America) |
| EAN-13 (GTIN-13) | 13 Digits | Retail Point-of-Sale (Global) |
| ITF-14 | 14 Digits | Shipping Cartons / Boxes (Not Retail) |
| Code 128 | Alphanumeric | Logistics, Tracking Labels, Inventory |
| QR Code | 2D Matrix | Marketing URLs, Menus, App Links |
How Scanners Work
Traditional laser scanners shoot a beam of light onto the barcode. The black bars absorb the light, while the white spaces reflect it back. The scanner measures the width of the reflected light pulses to decode the binary 1s and 0s into numbers.
Modern image scanners (like phone cameras) just take a picture and interpret the pattern digitally.
The "Check Digit" Magic
Why is the last number special? It prevents errors. It is calculated using the Modulo 10 algorithm:
- Sum the digits at odd positions & multiply by 3.
- Sum the digits at even positions.
- Add the two results together.
- The check digit is the number needed to make the total a multiple of 10.
Common Questions
Are UPC and EAN unique?
Yes. Because the US/Canada code (UPC) is effectively an international code (EAN) with a zero in front, they occupy the same global uniqueness registry. You never have to worry about a UPC duplicate conflicting with an EAN.
Which one should I use on Amazon?
If you are selling primarily in the US, select UPC. If you are selling globally, you can select EAN. Both are accepted, but sticking to your region's standard format is usually best to avoid confusion.
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