Choose the identifier
Select GTIN-8, GTIN-12, GTIN-13, GTIN-14, GLN-13, or SSCC-18 so the expected length is explicit.
Digits in · auditable check out
Calculate the final digit—and see why it fits.
Choose a supported GS1 identifier, enter digits, and calculate or validate its final check digit. CheckDigit shows the alternating weights, weighted sum, and Mod-10 remainder locally. It checks arithmetic integrity only—not assignment, ownership, authenticity, or a product record.
No lookup, scanning, barcode image, issuance, account, saved history, or indexed result URL.
Three visible steps
Choose, enter, verify
Enter digits only
Calculate from the data digits without the final digit, or validate the complete identifier including it. Leading zeroes are preserved.
Read the arithmetic
Inspect every weight, product, sum, remainder, and expected final digit instead of accepting an opaque answer.
Six fixed identifier formats
Match the length to the identifier
- Calculate or validate GTIN-8, GTIN-12, GTIN-13, and GTIN-14 check digits.
- Check the final digit of a 13-digit Global Location Number.
- Calculate or validate the final digit of an 18-digit SSCC.
- Learn exactly what arithmetic validation does not establish about an identifier.
Use your own digits
Keep the formula beside the answer
Choose the exact GS1 format, calculate or validate locally, and inspect every weighted step. CheckDigit does not send your identifier to a lookup service.