

Starting from the right side of the string, take every alternating digit and multiply it by 2. These are the steps that you need to follow to manually check the validity of any card number against the Luhn algorithm. To understand the working of the algorithm, let’s take a random card number as an example i.e.: You could do it in a couple of minutes using a pen and paper…if you wanted to. It may sound complicated but running the Luhn algorithm on any set of numbers isn’t actually that hard.
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How to Manually Check the Validity of a Credit Card Number Using the Luhn Algorithm

6 th to Second-to-Last Digit: All the digits, after the 6 th up till the second-to-last one, are generated uniquely for every cardholder.2 nd to 6 th Digits: The 2 nd, 3 rd, 4 th, 5 th and 6 th digits are used to identify the card issuer e.g., a bank branch.Some card networks use the first 2 digits as their identification as well.įor example, Visa cards always start with a ‘4’ whereas Amex cards always start with a ‘3’ which is immediately followed by either a ‘7’ or a ‘4’. The 1 st Digit: The first digit is the card network indicator.To understand the composition of a credit card number, we can break it down into four parts: What do the Digits on a Credit Card Number Mean? The calculation to compare a credit card number with your checksum is known as the Luhn algorithm. It gives merchants a way to verify the validity of a card number before accepting the customer's payment. Enter E-mail to get response? Submit How to do Credit Card ValidationĬredit card numbers are generated according to certain rules.
