Math Calculators

Luhn Algorithm Calculator

Check whether a credit card number passes the Luhn checksum algorithm used to catch typing errors.

Luhn checksum total —

Result —

About the Luhn Algorithm Calculator

The Luhn algorithm is a simple checksum formula used to validate identification numbers such as credit card numbers, catching most single-digit typos and transpositions.

Formula: starting from the rightmost digit, double every second digit (subtracting 9 if the result exceeds 9), then sum all digits — the number is valid if the total is a multiple of 10.

The Luhn check confirms a number is well-formed; it does not verify that a card actually exists or is active.