AkousaLuhn Check
Validate credit card and identification numbers using the Luhn algorithm.
About Luhn Check
The Luhn Check validates numbers using the Luhn algorithm (also known as the modulus 10 or MOD-10 algorithm), a simple checksum formula devised by IBM scientist Hans Peter Luhn in 1954 and now used to detect single-digit transcription errors in credit card numbers (Visa, Mastercard, Amex, Discover), IMEI device identifiers, Canadian SIN numbers, Israeli ID numbers, and several other identification systems. The algorithm alternately doubles every second digit from the right, sums all digits, and checks that the total is divisible by 10.
How to Use
Enter a number to validate — spaces and dashes are automatically stripped before processing. The tool applies the Luhn doubling and summation algorithm step-by-step, displays the digit-by-digit calculation table, and shows the final remainder to confirm pass (remainder 0) or fail. You can also enter an incomplete number without the final check digit and click Calculate Check Digit to compute the required last digit that would make the number Luhn-valid.
Common Use Cases
- Payment form developers implementing client-side credit card number validation using the Luhn check to detect obvious input errors before submitting to the payment gateway API and incurring a rejected transaction fee
- Mobile device management engineers verifying IMEI numbers scanned or manually entered by technicians to catch transposition errors during device enrollment in MDM platforms
- E-commerce and FinTech QA engineers generating Luhn-valid synthetic credit card numbers for use in payment gateway sandbox testing without using real card numbers
- Fraud detection analysts quickly checking whether suspicious credit card numbers from fraud reports or brute-force scanning attempts pass the Luhn check as a first-pass filter before deeper investigation
- Backend developers testing and validating their Luhn algorithm implementation by comparing the step-by-step calculation breakdown against their code's intermediate values to debug incorrect check digit results