Luhn Checksum Calculator
Enter a number and pick validate or compute check digit.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
The Luhn algorithm (also called the mod 10 algorithm) is a simple checksum formula used to catch accidental errors — a mistyped digit or two transposed digits — in identification numbers. Starting from the rightmost digit and moving left, every second digit is doubled; if doubling produces a two-digit number, its digits are added together (or 9 is subtracted, which is equivalent); all digits are then summed, and the number is valid only if that total is a multiple of 10.
This is the exact check built into credit and debit card numbers (ISO/IEC 7812), IMEI numbers for mobile devices, Canadian Social Insurance Numbers, and U.S. National Provider Identifiers — this calculator either validates a number you enter against the Luhn check, or, given a number missing its final digit, computes the one check digit that makes it pass.
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