1. What is a UPC-A Barcode?
The Universal Product Code (UPC-A) is the standard 12-digit barcode symbology used heavily in North America for retail point-of-sale tracking. Administered globally by GS1, it forms the backbone of inventory systems for major retailers, supermarkets, and online marketplaces like Amazon.
4. Interactive Generator Tool
UPC-A Generator
Batch Results
Pro Tip for Amazon Sellers
A UPC-A is required to list a product globally, but if you are physically sending boxes to an Amazon Fulfillment Center, the carton itself must be labeled with an FNSKU instead — and FNSKU labels use the Code-128 format, not UPC-A. See our full guide on creating Amazon FBA labels here.
2. The Anatomy of a UPC-A Code
Every UPC-A number is built from four functional blocks that always add up to exactly 12 digits. Here is the worked example used throughout this guide, 012345678905, broken into its parts:
(1 digit)
(6–10 digits total, incl. above)
(remaining digits)
(calculated)
3. The Math: How the Check Digit Is Calculated
You cannot pick the 12th digit yourself — it is the output of the Modulo-10 (Mod-10) algorithm, the same error-detection method used across the entire GS1 GTIN family. Its entire purpose is to catch human and scanner mistakes: if even one digit is mistyped or a laser misreads a smudged bar, the math will not add up and the scanner rejects the code instead of ringing up the wrong product.
Worked example — base number 01234567890:
| Position | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Digit | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 |
| Weight | ×3 | ×1 | ×3 | ×1 | ×3 | ×1 | ×3 | ×1 | ×3 | ×1 | ×3 |
- Odd positions (1,3,5,7,9,11): 0+2+4+6+8+0 = 20 × 3 = 60
- Even positions (2,4,6,8,10): 1+3+5+7+9 = 25
- Total: 60 + 25 = 85
- Round up to the next multiple of 10: 90
- Check Digit = 90 − 85 = 5 → Final code: 012345678905
5. The Step-by-Step Generation Workflow
Once your data is clean and your prefix is licensed, generating a full batch takes under a minute using the tool on this page:
- Open the Assign to My Business tab. Scroll back up to the generator and switch to the Bulk tab.
- Enter your GS1 Company Prefix. This is the number GS1 licensed to your business.
- Set a quantity or paste your product list. Either generate a straight sequential run, or paste product names so each one is labeled underneath its barcode.
- Click Generate Batch. The engine calculates every Modulo-10 check digit and renders each scannable symbol instantly in your browser — nothing is uploaded anywhere.
- Export your labels. Download a print-ready PDF sheet, grab a CSV of the raw codes for your inventory system, or print directly from the browser.