Credit Card Validator (Luhn)

About this calculator

This tool checks whether a card number is structurally valid using the Luhn algorithm, a checksum formula that doubles every second digit, adjusts values over 9, and sums the result to see if it lands on a multiple of 10. Every legitimate Visa, Mastercard, American Express and Troy card number is generated to satisfy this checksum, so a number that fails it is guaranteed to be mistyped or fake, though passing it does not prove the card is active or has funds.

It is used by developers testing payment forms and checkout flows without needing a real card, by customer support staff double-checking a number a customer read aloud over the phone, and by anyone who wants to catch a typo before submitting an order. The calculator also identifies the likely card network from the number's prefix and length, which is the same logic checkout pages use to show the right card-brand icon as you type.