Credit cards have 13 to 19 digits, depending on the card network
The number of digits on your credit card is not random. Most Visa and Mastercard cards carry 16 digits. American Express cards have 15 digits. Discover cards typically have 16 digits. Some business cards, store cards, and older cards may fall outside these ranges, but 15 or 16 is what you will see most often.
The digits are divided into groups that tell the card issuer, the card network, and the payment processor who you are and whether the card is valid. Understanding what each section means can help you spot fraud, fill out payment forms correctly, and know what information is actually sensitive.
Key Takeaways
- Most credit cards have either 15 digits (American Express) or 16 digits (Visa, Mastercard, Discover).
- The first digit identifies the card network — 4 for Visa, 5 for Mastercard, 3 for American Express, 6 for Discover.
- The first six digits together form the Bank Identification Number (BIN), which tells merchants and processors which bank issued the card.
- The last digit is a check digit that validates whether the card number itself is real, using a mathematical formula called the Luhn algorithm.
- The middle digits are your unique account number assigned by your bank.
What the first digit tells you
The very first digit on your card identifies the card network. This single number is called the Major Industry Identifier (MII). A 4 means Visa. A 5 means Mastercard. A 3 means American Express. A 6 means Discover.
You will see this digit used when you enter your card online or at a payment terminal — the system reads it when ready and knows which network to route your transaction through. This is why entering a Visa number into an American Express payment form will not work, even if you type the number correctly. The first digit does not match what the form expects.
The Bank Identification Number (BIN) and what it reveals
The first six digits of your card number together form the Bank Identification Number, or BIN. This six-digit code tells the merchant's bank which financial institution issued your card. If your card is a Chase Visa, the BIN will always start with Chase's assigned range. If it is a Bank of America Mastercard, the BIN will reflect that.
Merchants and payment processors use the BIN to route transactions to the correct bank and to check whether a card is legitimate. When you swipe or insert your card at a store, the terminal reads the BIN and confirms that a card with that number range actually exists. This is one reason why a card number that passes the check digit test (see below) can still be declined — the BIN itself may not be real.
The BIN also tells the processor what type of card it is — whether it is a standard credit card, a rewards card, a business card, or a prepaid card. This information helps merchants decide whether to accept it and what fees explore.
The account number in the middle
Digits 7 through 15 (or 7 through 14 on American Express) are your unique account number. This is the part that identifies you specifically within your bank's system. No two cardholders at the same bank will have the same account number in this section, even if they both have Visas.
Your bank assigns this number when the card is created. If you have multiple cards from the same bank, each one will have a different account number in this section. This is how the bank knows which card you are using and which account to charge the transaction to.
The check digit at the end
The last digit on your card is the check digit. It exists only to validate that the card number is mathematically real. The check digit is calculated using the Luhn algorithm, a formula that takes all the other digits and produces a single digit that should match the last one.
When you enter your card number online or at a terminal, the system runs the Luhn algorithm on the digits you entered. If the result does not match the last digit, the system knows the number is either fake or mistyped. This catches most typos and fraudulent card numbers before they are even sent to your bank.
You do not need to calculate this yourself — payment systems do it automatically. But it is why a card number that looks plausible can still be rejected when ready. The check digit failed.
Why card length varies
American Express uses 15 digits while Visa, Mastercard, and Discover use 16 because the card networks were designed at different times and made different choices about how much information to encode in the number itself.
American Express issues its own cards directly, so it does not need as much information to route transactions — the company already knows which of its own customers you are. Visa, Mastercard, and Discover are networks that work with thousands of banks, so they need more digits to identify which specific bank issued your card and which account you hold.
Some older cards, store cards, and business cards may have 13 or 14 digits instead. The principle is the same — the first digit identifies the network, the first six form the BIN, and the last digit is the check digit — but the account number section is shorter.
What you should and should not share
Your full card number is sensitive information and should never be shared except with merchants you trust or payment systems you initiated contact with. However, the first six digits (the BIN) are less sensitive — they are printed on receipts and visible to merchants, and they do not identify you personally.
The last four digits are also relatively low-risk. Banks and merchants often show you the last four digits to confirm which card you used, and this information alone cannot be used to make a purchase.
Never share your full card number, expiration date, and CVV together with anyone who contacts you first — not by email, phone, or text. Legitimate companies will never ask for this combination unsolicited.
Frequently Asked Questions
Why do some cards have more or fewer than 16 digits?
American Express cards have 15 digits by design, and some older or specialty cards may have 13 or 14. The variation comes from when the card network was created and how many banks it works with. Visa, Mastercard, and Discover standardized on 16 because they needed more digits to identify which of thousands of issuing banks created the card.
Can I tell what bank issued my card just by looking at the number?
Yes, partially. The first six digits (the BIN) tell you the bank. You can look up a BIN online using a BIN lookup tool to find out which bank issued the card. However, you cannot tell the cardholder's name, address, or account balance from the card number alone.
Is the check digit the same as the CVV?
No. The check digit is the last digit of the card number itself and validates whether the number is real. The CVV (Card Verification Value) is a separate three- or four-digit code printed on the back of the card that proves you physically have the card. They serve different purposes.
What happens if I type my card number wrong?
If you mistype a digit, the check digit will not match the rest of the number, and the payment system will reject it when ready as invalid. You will see an error message before the transaction is even sent to your bank. This is the check digit doing its job.
Do all credit cards follow the same digit structure?
The basic structure — first digit for network, first six for BIN, last digit for check digit — is the same across all major card networks. However, the total length varies, and some specialty cards (like corporate cards or prepaid cards) may have slightly different rules. The principle remains consistent.