Credit card issuers first assign the account numbers and then compute steps one through three of the Luhn algorithm to determine the appropriate check digit. In this case, the card number should ...

All mainstream credit card numbers obey a mathematical trick designed to catch the most common typos. It’s called the Luhn ...

The Luhn algorithm—also known as the “Modulus 10 algorithm”—is a formula used to determine the accuracy of credit card numbers.

The Luhn algorithm uses modulo-10 mathematics. To calculate the check digit, multiply every even-position digit (when counted from the right) in the number by two.

Credit card numbers aren't random, and they don't only identify your account. Here's how to decipher what your own credit card number means.

If the result is not a multiple of 10, then the credit card number is invalid. I’ll show the Luhn algorithm in action on my Visa, but you should try it with your credit card, too.