Math

Luhn Algorithm Calculator

Check a digit string with the Luhn checksum (credit-card style).

Valid?

This free Luhn Algorithm Calculator covers Check a digit string with the Luhn checksum (credit-card style).

Enter the Luhn Algorithm Calculator fields, then read the output. Math calculators on this site keep the formula visible beside the form.

Luhn Algorithm Calculator — how it works

Check a digit string with the Luhn checksum (credit-card style). Typical inputs are Digit string. How it works beside the form states the identity the Luhn Algorithm Calculator applies.

FAQ

How do I use the Luhn Algorithm Calculator?

Open the Luhn Algorithm Calculator, fill Digit string, and read the result. Double every second digit from the right; subtract 9 if over 9; total must be divisible by 10.

What formula does the Luhn Algorithm Calculator use?

The Luhn Algorithm Calculator uses the identity in How it works. In words: Double every second digit from the right; subtract 9 if over 9; total must be divisible by 10.

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