How Credit Cards Work

By: Melanie Radzicki McManus  | 

What Credit Card Numbers Mean

The front of your credit card has a lot of numbers — here's an example of what they might mean.
Illustration by Rosaleah Rautert

Although phone companies, gas companies and department stores have their own numbering systems, ANSI Standard X4.13-1983 is the system used by most national credit card systems.

Here are what some of the numbers stand for.


The first digit in your credit card number, the major industry identifier (MII), signifies the system.

Here are the major MIIs, along with examples of the most popular cards using a particular number:

  • 3 - Travel and entertainment/American Express or Diners Club
  • 4 - Banking and financial/Visa
  • 5 - Banking and financial/Mastercard
  • 6 - Banking and merchandising/Discover

Most consumers will only have credit cards that start with one of these four numbers, unless they have store-specific credit cards, which follow different rules. The structure of the card number varies by system. For example, American Express card numbers start with 34 or 37; Discover with 65, 644, 6011.

A card's MII, plus the five digits following, are called the issuer identification number or the bank identification number. Together, these tell you which credit card company issued the card and what network it belongs to, plus indicate which benefits it carries for the cardholder. For example, the initial digits 414709 mean the card is a Capital One Signature Visa.

The next several digits before the final one, which generally range from seven to 10, comprise your individual account number. And that last digit? It's called the checksum, and lets people or computers know if the number is valid. This helps catch both numbers that are incorrectly entered and fake ones generated by scammers.