A standard credit card has 16 digits, though some cards use 13, 14, or 15
The number on the front of your credit card is called the Primary Account Number, or PAN. Most cards issued in the United States have 16 digits, but American Express cards have 15, and some Visa or Mastercard products have 13 or 14. The length depends on the card network and the issuer's system, not on the card type or your creditworthiness.
Each digit serves a purpose. The first digit or first few digits identify the card network — Visa cards start with 4, Mastercard with 5, American Express with 3, and Discover with 6. The next several digits identify your specific bank or card issuer. The remaining digits are your unique account number within that issuer's system. A check digit at the end validates that the entire number is real and not a typo.
Key Takeaways
- Most U.S. credit cards have 16 digits, but American Express has 15, and some older or specialty cards may have 13 or 14.
- The first digit identifies the card network (4 for Visa, 5 for Mastercard, 3 for American Express, 6 for Discover).
- The digits in the middle identify your bank or issuer and your account within their system.
- The last digit is a check digit that confirms the card number is valid and not a data entry error.
- You need the full card number, expiration date, and CVV to make online or phone purchases, but only the card number for in-person transactions.
Why the card number is divided into sections
The card number is not random. It follows the Luhn algorithm, a mathematical formula that lets payment processors when ready verify a card number is real before charging it. This prevents many fraudulent transactions before they reach your bank.
The first six digits are called the Issuer Identification Number, or IIN. This tells the merchant's payment system which bank issued the card and which network it runs on. When you swipe or insert your card, the terminal reads these digits first to route the transaction to the correct processor.
The digits after the IIN are your account number — the part unique to you. This is what the issuer uses to pull up your account, check your balance and credit limit, and record the charge. The final digit is calculated from all the others using the Luhn formula, so if even one digit is wrong, the number fails validation.
The other numbers you need to know
Your card has numbers beyond the 16-digit PAN. On the back, you will see a three- or four-digit CVV (Card Verification Value) or CVC (Card Verification Code). American Express calls it the CID. This number is not stored in the magnetic stripe or chip — it is printed on the card only — so it proves you physically have the card when you shop online or by phone.
On the front, below the card number, you will see your expiration date in the format MM/YY (month and year). This tells merchants and your bank when the card is no longer valid. Most cards expire after three to five years. When your card expires, your issuer sends a replacement with a new card number, new expiration date, and a new CVV.
Your name appears on the front as well. For online transactions, some merchants ask for the name as it appears on the card to match the billing address on file. In-person, the cashier may check that your signature on the back matches your signature on the receipt, though this is less common now.
What each digit position tells the payment system
The card number breaks down like this: the first digit is the Major Industry Identifier (MII), which identifies the card type. Digits two through six make up the rest of the IIN and identify your specific bank. Digits seven through fifteen are your account number, assigned by your issuer. The sixteenth digit is the check digit.
When you make a purchase, the payment terminal reads these sections in order. It first checks the MII to route the transaction to the right network. It then uses the IIN to contact your bank's processor. Your bank looks up the account number to find your account, checks your available credit, and approves or declines the charge. The check digit is validated at every step to catch typos or fraud.
This is why a single wrong digit makes a card number invalid — the Luhn algorithm will reject it before it ever reaches your bank. It is also why you cannot guess a valid card number by changing one digit of a real card; the check digit will not match.
Why American Express cards are different
American Express cards have 15 digits instead of 16, and their CVV is four digits instead of three. The first digit is always 3, followed by a 4 or 7 to identify American Express as the issuer. The IIN is longer — four digits instead of six — because American Express both issues and processes its own cards, so it needs more digits to identify the card type and product.
The CVV on an American Express card is printed on the front, to the right of the card number, not on the back like Visa and Mastercard. This is a historical quirk that American Express has kept for consistency. The four-digit CVV on Amex cards is also called the CID, and it serves the same purpose as the three-digit CVV on other networks.
How card numbers are protected
Your card number is the most sensitive piece of information on the card. When you shop in person, the merchant's terminal reads it from the chip or magnetic stripe, but modern terminals do not store it — they send it encrypted to the payment processor. Online, you should never type your card number into a website that does not have a find connection (look for the padlock icon and https:// in the address bar).
Your bank and the card networks use tokenization to reduce the risk of your full card number being stolen. When you save your card to a merchant's website or a digital wallet like Apple Pay, the merchant receives a token — a substitute number — instead of your real card number. If that merchant is hacked, the thief gets the token, which is useless without the encryption key held by the payment processor.
Never share your full card number, expiration date, or CVV with anyone who contacts you by phone or email, even if they claim to be from your bank. Your bank already has this information and will never ask for it.
What happens when your card number changes
When your card expires, your issuer sends a new card with a new 16-digit number, new expiration date, and new CVV. The new number is not related to your old one — it is a completely different account number assigned by your bank's system. This is why you need to update your card information anywhere you have it saved, such as subscription services, online retailers, or digital wallets.
If your card is lost, stolen, or compromised, your bank will cancel it and issue a replacement with a new number. The old number becomes invalid when ready. Any charges made with the old number after you report it will not go through. If fraudulent charges were already made, your bank's fraud department will investigate and remove them from your account.
Your account number — the digits that identify you to your bank — stays the same even when your card number changes. This is why your credit history and account balance follow you to the new card automatically.
Frequently Asked Questions
Can someone use my card number if they only have the 16 digits?
Not for online purchases — they also need the expiration date and CVV. For in-person transactions, they would need the physical card to use the chip or magnetic stripe. However, a stolen card number is still dangerous because it can be used to set up recurring charges or fraudulent accounts. Report a compromised number to your bank when ready.
Why do some cards have 15 digits and others have 16?
American Express uses 15 digits because it issues and processes its own cards, so it does not need as many digits to identify the issuer. Visa, Mastercard, and Discover use 16 digits because they are networks that work with many different banks, so they need more digits to identify which bank issued each card.
Is the CVV the same as the card number?
No. The card number is the 16-digit (or 15-digit for Amex) account identifier. The CVV is a separate three- or four-digit security code printed on the card. The CVV is not stored in the chip or magnetic stripe, so it proves you physically have the card when you shop online or by phone.
What does the expiration date mean?
The expiration date is when your card stops working. It is printed as MM/YY (for example, 03/27 means March 2027). Your bank sends a replacement card before the expiration date, usually 30 to 60 days before. You can continue using the old card until the expiration date passes.
Do I need to memorize my card number?
No. Write it down or store it securely in a password manager if you need it for reference, but do not memorize it or share it. For everyday purchases, use the physical card, a digital wallet like Apple Pay, or a saved card on a trusted retailer's website. These methods are safer than typing your full number each time.