Quick answer
A check digit is calculated from the other digits and included to detect common data-entry and scanning errors. Different formats use different weighting and modulo rules. Validation confirms internal consistency; it does not prove that the identifier is issued, owned, or attached to the correct item.
How to do it
- Select the exact identifier format.
- Enter the data digits without decorative punctuation.
- Calculate or validate, then compare the complete value with the source record.
Errors checksums catch
Well-designed check-digit systems catch all single-digit errors and many adjacent transpositions, but not every possible substitution. They are an inexpensive integrity check, not cryptographic protection and not a database lookup.
Keep identifiers as text
Leading zeros are significant in UPC, GTIN, and many internal codes. Spreadsheet and database numeric types can strip zeros or display scientific notation. Store the identifier as a string and calculate only from its digit characters.
Common mistakes to avoid
- Using the EAN formula for a different symbology.
- Including spaces or hyphens as data digits.
- Equating a valid check digit with a registered product.
Try the related tool
Use QRFoundry directly in your browser. Tool inputs and uploaded files are processed on your device.
Open Check Digit Calculator