What is a credit card number?

Ever wondered what the numbers on your credit card mean? Each of those digits is necessary for transactions to take place. The numbers are used to authenticate things like the identity of the cardholder and the credit card issuer.

Credit card numbers follow a formula that’s based on the credit card issuer and network. Learn more about what these numbers mean and where to find them.

What you’ll learn:

• Credit card numbers identify the credit card network, credit card issuer and cardholder.

• Other numbers you might see on a credit card are the security code and expiration date.

• Because of potential credit card scams, it’s important to help protect yourself from fraud.

• Some credit card issuers allow you to use virtual card numbers. This can help protect your credit card information when making online purchases.

A credit card number is the 15- or 16-digit number found on the front or back of a credit card. It identifies several things, including:

• The credit card network: The four major credit card networks in the U.S. are Visa®, Mastercard®, American Express® and Discover, which Capital One recently acquired. These networks communicate between merchants and credit card issuers to facilitate credit card purchases.

• The credit card issuer: A financial institution that provides credit to cardholders, like Capital One. Two of the major credit card networks are also credit card issuers. That includes Discover.

• The cardholder: The cardholder is the person to whom a credit card is issued. 

The number on your credit card is different from your account number, although the two are linked. For example, if your credit card is lost or stolen, you’ll receive a new card with a different credit card number. But the account number will stay the same.

While they might seem random, the digits on your credit card signify the major industry identifier (MII), issuer identification number (IIN), account identifier and checksum.

The first six to eight digits are referred to as the bank identification number (BIN) or the IIN. These numbers identify the card issuer. The remaining digits identify the individual account of the cardholder.

Because each digit has meaning, it’s crucial to protect your credit card number. Avoid writing down or taking photos of the number, and always report a lost or stolen credit card to the card issuer.

Here’s a breakdown of what each number means:

The first digit on a credit card will tell you two things: the credit card network and the industry associated with the card. For example, credit cards starting with a 3 are from American Express, while credit cards starting with a 4 are from Visa. 

Depending on the type of card, the first digit also identifies which industry the card is associated with. This digit is the MII.

This chart lists the numbers’ corresponding networks and MIIs:

The next five to seven digits form the rest of the BIN. These IINs can identify the credit card issuer and even the specific type of credit card.

These digits form a unique sequence to identify the account and cardholder. This number may change if you get a new card.

The last digit is known as the checksum or check digit. During the transaction process, this number is quickly plugged into a formula called the Luhn algorithm and used to ensure the card number is valid.

In addition to the credit card number, your credit card also contains the expiration date and security code. Here’s what to know about each:

A credit card expiration date shows when the card is no longer valid and when it will need to be replaced. While your credit account will continue after this date, you will need a new physical card to be able to use it. 

Expiration dates are generally formatted with two digits for the month and two digits for the year, separated by a forward slash. An expiration of September 2028 would look like 09/28 on your card, for example. And it means the card should be active through the last day of September 2028.

A credit card expiration date also helps maintain security for your account. Entering a card expiration date can help prevent credit card fraud by adding another level of verification during purchases. And because credit cards suffer wear and tear, the expiration date ensures you get a fresh card, with any new security measures, every few years.

Sometimes called the card verification value (CVV) or card verification code (CVC), this three- or four-digit number offers additional verification for remote purchases. Retailers aren’t able to store CVV numbers, which means the code can help protect your credit account in case of a data breach. The security code can be found on the front or back of the card, depending on the issuer.

Here are some ways to help protect yourself from credit card fraud:

• Monitor your account information online and offline. Monitoring your credit scores, credit reports and credit card statements can help you notice if something isn’t right. Keep an eye out for any suspicious activity, like transactions you didn’t make.

• If you hold on to physical documents, store them in a secure location. You can also shred papers before they’re tossed in the trash. And if you cancel a credit card account, make sure to destroy the card before throwing it away.

• Boost your digital defenses. Using a virtual private network (VPN) on your computer or smartphone can help prevent others from stealing your financial information through a public Wi-Fi network. Strong passwords for each of your online accounts can also help. And you could enable two-factor authentication for even more protection.

• Use a virtual card. Virtual card numbers are another way to keep your credit card account more secure. These are unique credit card numbers linked to your credit card account that allow you to shop online without giving merchants your physical credit card number.

Here are the answers to some commonly asked questions about credit card numbers:

Credit card numbers are a string of digits on the front or back of a credit card that identify the card issuer, card network and cardholder. Because credit card numbers contain important identifying information, it’s important to keep your card number safe and keep security in mind when using it.

Interested in getting a new credit card? Check out Capital One’s comparison tool to find out which cards may be best for you. You could also see whether you’ll be approved for card offers without any impact on your credit scores.