Credit cards have 16 digits in most cases, though some have 14 or 15
The standard credit card number in the United States is 16 digits long. Visa, Mastercard, and Discover cards all use 16 digits. American Express cards are shorter — they have 15 digits. Some older or specialty cards may have 14 digits, but this is less common now.
The digits are not random. Each one serves a purpose, and the pattern tells you something about the card issuer, the bank, and whether the number is valid. Understanding what those digits mean can help you spot errors when you enter your card information online or verify that a card number makes sense before you use it.
The card number is printed or embossed on the front of your card, usually in four groups of four digits. On the back, you will find a three- or four-digit security code (called the CVV or CVC) that is separate from the main card number.
Key Takeaways
- Most credit cards have 16 digits; American Express has 15; the first digit identifies the card network (Visa, Mastercard, Discover, or Amex).
- The first six digits are the bank identification number (BIN), which tells you which bank or financial institution issued the card.
- Digits 7 through 15 (or 14 for some cards) are your unique account number assigned by your bank.
- The last digit is a check digit calculated using the Luhn algorithm, which helps detect typos or fraud.
- The security code on the back (CVV or CVC) is separate from the card number and has three or four digits depending on the card type.
What the first digit tells you
The very first digit of your card number identifies the card network. This digit is called the Major Industry Identifier (MII). If your card number starts with a 4, it is a Visa card. If it starts with a 5, it is a Mastercard. A 6 means Discover. American Express cards start with a 3 (either 34 or 37).
This first digit is one reason why some websites can tell you which card type you are using as soon as you type the first number. The merchant does not need to wait for all 16 digits — the first one is enough to know whether to show Visa, Mastercard, or Discover logos.
The bank identification number (digits 1 through 6)
The first six digits together form the Bank Identification Number (BIN), also called the Issuer Identification Number (IIN). These six digits tell you which bank or financial institution issued your card. Different banks have different BIN ranges assigned to them by the card networks.
When you make a purchase, the merchant's payment processor uses the BIN to route your transaction to the correct bank for approval. The BIN also helps banks and fraud detection systems identify which institution issued the card, which is useful when investigating disputes or suspicious charges.
You do not need to memorize your BIN, but it is useful to know that the first six digits are not unique to you — many cardholders from the same bank will share the same BIN. Your unique account number comes after.
Your account number (digits 7 through 15)
Digits 7 through 15 make up your unique account number. This is the part of the card number that identifies your specific account at your bank. No other cardholder has this exact sequence of digits (though the BIN portion may be shared with thousands of other customers of the same bank).
The length of the account number varies slightly depending on the card type. On a standard 16-digit Visa or Mastercard, you have nine digits for your account number. On a 15-digit American Express card, you have nine digits as well. This is why the total length differs between card types — the account number portion stays roughly the same size, but the overall card number length changes.
The check digit (last digit)
The final digit of your card number is a check digit. This digit is calculated using a mathematical formula called the Luhn algorithm. The check digit does not represent any information about you or your account — it is purely a validation tool.
When you enter your card number online or at a payment terminal, the system runs the Luhn algorithm on the first 15 digits to calculate what the last digit should be. If the last digit you entered matches the calculated digit, the card number passes the basic validity check. If it does not match, the system knows there is a typo or the number is fraudulent.
This check catches most accidental errors — if you transpose two digits or mistype one number, the check digit will not match and the transaction will be rejected before it even reaches your bank. It is not a security feature (anyone can calculate a valid check digit), but it is a useful error-detection tool.
The security code on the back (CVV or CVC)
The three- or four-digit code on the back of your card is separate from the card number itself. Visa and Mastercard call this the CVV (Card Verification Value). American Express calls it the CVC (Card Verification Code). Discover uses CVV as well.
This code is not embossed or printed as part of the main card number — it appears only on the back (or front, in the case of American Express). Because it is not stored in the magnetic stripe or chip, a merchant who only has your card number cannot use it without also having physical access to the card itself. This makes the CVV a useful fraud prevention tool for online and phone purchases.
The CVV is three digits for Visa, Mastercard, and Discover. American Express uses four digits. You should never share this code with anyone except during a legitimate purchase, and legitimate merchants will never ask you to provide it over email or phone.
Why card length varies between networks
Visa, Mastercard, and Discover settled on 16 digits as a standard, but American Express chose 15 digits when it designed its card system. This difference reflects different decisions about how to structure the BIN, account number, and check digit.
American Express also issues its own cards directly (rather than through partner banks the way Visa and Mastercard do), so it has a different need for the BIN structure. The 15-digit format has worked for American Express for decades and remains their standard.
Some older cards or specialty cards may have 14 digits, but these are increasingly rare. If you encounter a card with an unusual length, it is usually a legacy card or a card issued outside the United States.
Frequently Asked Questions
Is my card number the same as my account number?
No. Your card number is 16 digits (or 15 for American Express) and includes the bank identification number, your account number, and a check digit. Your account number is just one part of the card number — typically digits 7 through 15. Your bank may also assign you a separate account number for your checking or savings account, which is different from your credit card number.
Can someone use my card if they only have the card number?
For online purchases, they would also need the expiration date and CVV code from the back of the card. For in-person purchases, they would need the physical card itself. If someone has your full card number, expiration date, and CVV, they can make online purchases without the card. This is why you should never share these details via email or over the phone unless you initiated the contact with a merchant you trust.
What does it mean if my card number is rejected?
The most common reason is a typo — you may have entered a digit incorrectly, which would cause the check digit validation to fail. Other reasons include an expired card, a card that has been reported lost or stolen, insufficient funds, or a merchant system error. If you are certain you entered the number correctly, contact your card issuer to confirm the card is active.
Do all credit cards have 16 digits?
No. American Express has 15 digits. Some specialty cards, store cards, or older cards may have 14 digits. Debit cards and prepaid cards may also vary in length. The 16-digit standard applies to most major credit cards (Visa, Mastercard, Discover) issued in the United States, but it is not universal.
Why does my card number start with a different digit than my friend's card?
The first digit identifies the card network. If your card starts with 4 and your friend's starts with 5, you have a Visa and they have a Mastercard. If both cards are from the same network but the first six digits differ, you have different banks as your card issuer. The first digit alone tells you the network; the first six digits tell you the specific bank.