GTIN Checker — UPC / EAN / ISBN Validator
Check retail barcodes against the GS1 check-digit algorithm — EAN-8, UPC-A, EAN-13, and GTIN-14 — with format detection, country prefix lookup, and UPC↔GTIN conversion. Everything runs in your browser.
GS1 check digit calculator
Enter the digits without the check digit — the full code is returned. Works for GTIN-8, UPC-A, EAN-13, and GTIN-14.
UPC ↔ GTIN converter
Paste any barcode to see every equivalent format. Leading zeros never change the check digit — a UPC-A is just a GTIN-14 without them.
ISBN-10 validator
How it works: starting from the digit left of the check digit, weights alternate 3, 1, 3, 1 moving right-to-left. The check digit brings the weighted sum to the next multiple of 10 — the same formula across UPC-A, EAN-8/13, and GTIN-14.
A valid check digit confirms the number is well-formed, not that it was issued by GS1 to your brand. Marketplaces like Amazon cross-check the GS1 registry — reseller codes can pass the checksum and still be rejected.
Frequently asked questions
What is the difference between UPC, EAN, and GTIN?
GTIN is the umbrella identifier in the GS1 system. UPC-A (12 digits) is the North American variant, EAN-8 and EAN-13 are the international retail formats, and GTIN-14 is the 14-digit superset used on cases and pallets. They are the same numbering system — shorter codes are simply zero-padded to GTIN-14.
How do I convert UPC to GTIN-14?
Pad the UPC-A with leading zeros to 14 digits. The check digit does not change, because GS1 weights are counted from the rightmost data digit. Use the converter above — it shows every equivalent format and re-verifies each one.
Does a valid check digit mean the barcode is registered?
No. The checksum only proves the digits are well-formed — it says nothing about whether GS1 issued the number or who owns it. Marketplaces like Amazon cross-check the GS1 registry and brand ownership, so a checksum-valid code can still be rejected as unregistered or mismatched.
Can I look up which company or product a GTIN belongs to?
Not from the digits alone. A GTIN encodes a GS1 prefix (which identifies the issuing country organization, shown in the result above), a company prefix, and an item reference — but mapping those to a company name requires the GS1 registry (GEPIR) or a licensed product database. This tool verifies the number is structurally valid; ownership lookup is a separate registry query.
How do I calculate a GTIN check digit by hand?
Starting from the rightmost data digit, multiply digits alternately by 3 and 1 moving right-to-left, then sum. The check digit is whatever brings the total to the next multiple of 10. The calculator above does this for you — enter the code without its last digit and it returns the complete GTIN.
What does the check digit actually catch?
Single mistyped digits and most adjacent-digit transpositions — the classic data-entry errors when someone keys a barcode by hand. It is an integrity check, not a security feature: the algorithm is public and trivially reproducible.
Can I validate ISBNs here too?
Yes. ISBN-13 is just an EAN with a Bookland prefix (978 or 979) and validates with the same GS1 check digit — paste one into the main field. The separate ISBN-10 box below uses the older mod-11 checksum and also shows the ISBN-13 equivalent.
Is my barcode data uploaded anywhere?
No — every check runs in your browser. Nothing is sent to a server, logged, or stored, so pre-launch product codes stay private.