Text & writing
Luhn checksum calculator
Generate or verify a modulo-10 check digit on a numeric string.
A clear answer. Here’s how.
Doubles every second digit from the right, beginning with the rightmost body digit before the check digit. Adds decimal digits of doubled values and chooses a check digit making the total divisible by 10. Accepts up to 100 body digits and retains zeros. A passing checksum is arithmetic only and does not verify an account, issuer, ownership or valid allocation.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Operation
- Validate complete value
- Numeric value
- 79927398713
Example result
- Luhn check digit
- 3
- Complete value
- 79927398713
- Supplied checksum
- Passes
Alternates doubling from the rightmost body digit, summing the digits of doubled values. Checksum arithmetic only; it does not verify an account, issuer or valid allocation.