A GTIN (Global Trade Item Number) is the umbrella term GS1 uses for the family of product identifiers you'll see as EAN-8, UPC-A (GTIN-12), EAN-13 (GTIN-13) and GTIN-14. They're the same numbering system at different lengths, and every valid code carries a check digit computed from the digits in front of it, so you can convert between lengths without breaking that checksum.

This tool detects which format a code is in, validates its check digit, and converts it to the other three lengths - plus a GTIN-14 packaging conversion that uses a real GS1 indicator digit instead of just padding with a zero.

When you'd use this

Most often: a supplier hands you a 12-digit UPC and your system wants a 13-digit EAN, or a marketplace CSV rejects a barcode because it's the wrong length for the field. Converting by hand means re-deriving the check digit correctly, which is where manual conversions usually go wrong.

It's also useful for building GTIN-14 case/pallet codes for shipping labels, where the leading digit is a real GS1 packaging indicator (1–8) or the variable-measure indicator (9), not just a placeholder zero.

Common errors

"Checksum mismatch" means the last digit of the code you pasted doesn't match what GS1's check-digit algorithm computes from the rest - either it was mistyped, or it isn't a real GTIN at all.

"Cannot convert without losing significant digits" appears when you try to shorten a code (say, GTIN-14 → GTIN-12) but the digits being stripped aren't all zeros. That's not a bug - it means the code genuinely doesn't have a valid shorter representation, because a non-zero digit in that position is meaningful.

Frequently asked questions