Free FBA tool
UPC & Barcode Validator
Barcode
Paste a 12-digit UPC-A, 13-digit EAN-13, 8-digit EAN-8, or 14-digit GTIN. Spaces and hyphens are fine. Enter 11 digits (UPC-A) or 7 digits (EAN-8) to compute the missing check digit.
Valid barcode
Valid UPC-A. The check digit (2) matches the GS1 formula.
Format: UPC-A
This checks the check-digit math only. It does not confirm the code is registered to your brand in the GS1 database, which Amazon also verifies on most new listings. A reseller barcode can pass this test and still be rejected.
Digit breakdown
The highlighted last digit is the check digit, computed from the others by the GS1 formula.
Inventory Hero
Keep your catalog clean, not just your barcodes
A valid GTIN is step one. Inventory Hero keeps your product catalog, costs, and inventory in one place, so the identifiers, pack sizes, and landed costs behind every SKU stay correct as you add products and restock.
- One source of truth for SKUs, GTINs, and pack sizes
- Costs and inventory tied to each product
- Less spreadsheet drift as your catalog grows
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How the check digit works
The GS1 mod-10 formula
Take every digit except the last. Starting from the right, multiply them by 3, 1, 3, 1, and so on. Add the results. The check digit is the number that brings that sum up to the next multiple of 10: check = (10 - (sum mod 10)) mod 10. The same rule works for UPC-A, EAN-13, EAN-8, and GTIN-14 because the weighting is anchored to the right.
Worked example
Take the UPC-A 036000291452. (It is a real GS1 sample code, used here only to show the math; list your own products with your own GTIN.) Drop the last digit and compute the check digit from the first eleven, 03600029145.
- Weight from the right: 0,3,6,0,0,0,2,9,1,4,5 times 3,1,3,1,3,1,3,1,3,1,3
- Weighted sum: 0 + 3 + 18 + 0 + 0 + 0 + 6 + 9 + 3 + 4 + 15 = 58
- Check digit: (10 - (58 mod 10)) mod 10 = (10 - 8) = 2
- Full code: 036000291452, which is valid
Change any single digit and the sum no longer lands on a multiple of 10, so the code fails, which is exactly how the check digit catches a typo before it becomes a rejected listing. Once your barcode checks out, price the listing with the FBA fee calculator before you finalize it.
Key terms
- Check digit
- The last digit of a UPC/EAN/GTIN, derived from the others by the GS1 formula. It exists to catch a mistyped or transposed digit before the code is used.
- GTIN
- Global Trade Item Number, the umbrella term for GS1 product barcodes. UPC-A (12), EAN-13 (13), EAN-8 (8), and GTIN-14 (14) are all GTINs.
- FNSKU
- Amazon's fulfillment label for your physical units (often starting with X00). It is not a GTIN and has no check digit, so it cannot be validated here.
Frequently asked questions
How do I check if a UPC is valid?
A UPC, EAN, or GTIN is valid when its last digit, the check digit, matches the value the GS1 formula produces from the digits before it. Paste the full number above and the validator recomputes the check digit and compares it. A single mistyped or transposed digit makes the whole code invalid, which is the most common reason a barcode is rejected.
What is a check digit and how is it calculated?
The check digit is the final digit of a UPC/EAN/GTIN, and it exists to catch typos. To compute it, start from the digit immediately left of the check digit, weight it by 3, then alternate 1, 3, 1, 3 moving left; add the weighted digits, and the check digit is whatever brings that sum to the next multiple of 10. For the UPC-A 03600029145, the weighted sum is 58, so the check digit is 2, making the full code 036000291452.
What is the difference between a UPC, EAN, and GTIN?
They are all GS1 barcodes built on the same check-digit math, just different lengths. UPC-A is the 12-digit code common in North America. EAN-13 is the 13-digit international version, and EAN-8 is its 8-digit short form. GTIN-14 is the 14-digit code used on cases and cartons. This tool validates all four, and Amazon accepts UPC and EAN as product GTINs.
Do I enter the 12-digit UPC or the 13-digit EAN in Seller Central?
Amazon accepts either. When you create a new product, the Product ID field is labeled UPC/EAN/GTIN, and you enter whichever full, valid code you own: a 12-digit UPC-A or a 13-digit EAN-13. You do not pad or convert one into the other; enter the code exactly as GS1 issued it, leading zeros included, and confirm it passes the check-digit test first.
Is an FNSKU or ASIN the same as a UPC?
No. An ASIN (a 10-character code like B08N5WRWNW) is Amazon's internal product identifier, and an FNSKU (which usually starts with X00) is the label Amazon puts on your physical units in its warehouse. Neither is a GS1 barcode and neither has a UPC check digit, so this validator flags them rather than testing them. If you copied a code off an already-labeled unit and it starts with X00, that is the FNSKU, not the product barcode you list with. You still need a real UPC or EAN GTIN to create most new listings.
Does Amazon require a GS1 barcode, and will a valid check digit be enough?
For most new listings Amazon requires a GTIN (a UPC or EAN), and a valid check digit alone is not enough: Amazon cross-checks the GS1 database to confirm the barcode's prefix was issued to your brand. So a cheap code from a barcode reseller can pass the check-digit test here and still get your listing rejected, because the prefix belongs to the reseller, not you. Your real options are to buy GS1-issued codes directly from GS1 (gs1.org / GS1 US), or, if you are Brand Registered, apply for a GTIN exemption for your own private-label products, though some categories such as grocery, health, and beauty do not grant it. Either way the code still has to pass the check-digit test, which is what this tool confirms.
Inventory Hero
A clean catalog, from barcode to bottom line
Inventory Hero keeps the identifiers, costs, and stock behind every SKU in one place, so a valid GTIN is just the start of a catalog you can actually run your business on.
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<p style="font:13px/1.5 system-ui,sans-serif;text-align:center;margin:8px 0 0"><a href="https://www.inventoryhero.ai/tools/upc-barcode-validator">UPC & Barcode Validator</a> by Inventory Hero</p>See all our free Amazon FBA calculators.