Credit card numbers have presented a bit of a mystery to many people. In fact, it is not uncommon for someone to ask how long we have before we run out of card numbers. After all, there are only so many combinations of 16-19 digits, right? What do the numbers mean? Are they all random? Hopefully, this post will provide some quick answers to those questions.
Are card numbers random? The answer is, “sort of.” The first six digits in the account number are the Bank Identification Number, or BIN. Of those, the first two numbers represent the type of card – Visa, MasterCard, American Express, Discover, and Diners’ Club. For example, a card that begins with 37 is an American Express card. The account number follows the first six and is usually comprised of 7-12 digits and the last number is called a check digit. The structure of the account number is determined by ISO 7812.
Will we run out of credit card numbers? The short answer is “no.” While it might seem that the information above limits the number of accounts numbers that could be issued by a single card issuer, the fact is that it is sufficiently flexible to allow for a very large number of cards to be issued with unique numbers. For example, if we assume that each issuer provides a 9 digit account number, that means that for each BIN (and an issuer may have many) they can issue 1,000,000,000 unique numbers. So if an issuer has 6 BINs, that is a range of approximately 6,000,000,000 unique numbers that could be issued. Failing all else, if we find that we are running out of numbers within the current constraints, the account number itself could be lengthened by one or more digits.
While it may not always seem so, almost every aspect of the payment card (a generic term for both credit and debit cards) is very carefully standardized to ensure greater acceptance. The size of the card, the length of the account numbers and even where certain elements are placed on the card, are carefully prescribed so that the card can be accepted at the largest number of merchants possible.