Credit cards have 13 to 19 digits, depending on the card network
The number on the front of your credit card is called the Primary Account Number, or PAN. Most cards issued today have 16 digits, but the range is 13 to 19. Visa cards are typically 16 digits. American Express cards are 15 digits. Discover and Mastercard cards are usually 16 digits. The exact length depends on which bank issued the card and which payment network (Visa, Mastercard, American Express, Discover) processes the transaction.
The digits are not random. Each one serves a specific purpose, and the sequence follows a mathematical rule that helps detect errors and fraud. Understanding what these numbers represent can help you spot counterfeit card details and understand how your card information is used when you make a purchase.
Key Takeaways
- Most credit cards have 16 digits, but Visa and Discover cards can range from 13 to 19, while American Express cards have exactly 15 digits.
- The first digit identifies the card network (4 for Visa, 5 for Mastercard, 3 for American Express, 6 for Discover), and the first six digits together identify your bank.
- The last digit is a check digit calculated using the Luhn algorithm, which detects whether a card number has been entered or transmitted correctly.
- The middle digits are your unique account number assigned by your bank, and they never change for the life of that card.
What each section of digits represents
The credit card number breaks down into four distinct parts. The first digit is the industry identifier. A 4 means Visa, a 5 means Mastercard, a 3 means American Express, and a 6 means Discover. This single digit tells any merchant or payment processor which network will handle the transaction.
The first six digits together are called the Bank Identification Number, or BIN. These digits identify your specific bank or credit card issuer. For example, if your card starts with 453210, the 453210 is the BIN. Payment processors use the BIN to route your transaction to the correct bank and to check whether the card is valid. You can look up a BIN online to see which bank issued a particular card, though the full card number itself is private.
The middle digits (digits 7 through 15 on a 16-digit card) are your account number. Your bank assigns this number to your specific account. It never changes as long as you hold that card. If you close the card and the bank reissues it, you get a new account number.
The last digit is the check digit. It is calculated from all the other digits using a mathematical formula called the Luhn algorithm. When you enter your card number online or at a terminal, the payment system runs the Luhn check to make sure you typed it correctly. If the check digit does not match, the transaction is rejected before it even reaches your bank. This catches typos and prevents some fraud.
Why card length varies by network
American Express uses 15 digits because it was designed differently from other networks. Amex issues its own cards and processes its own transactions, so it does not need to follow the same standards as Visa and Mastercard, which are networks that multiple banks use. The 15-digit format has been Amex's standard since the company began issuing cards.
Visa, Mastercard, and Discover use 16 digits most of the time, but the standard allows for variation. Visa cards can legally be 13, 16, or 19 digits. Most Visa cards in circulation are 16 digits, but some older cards or cards issued in certain regions may be 13 or 19. The variation exists because the standard was designed to be flexible as the payment industry evolved.
The length difference does not affect how you use the card. A 15-digit Amex works the same way as a 16-digit Visa. The length is an internal detail that matters to payment processors and fraud detection systems, not to you as a cardholder.
The Luhn algorithm and check digit
The last digit on your card is not part of your account number. It is a check digit calculated using the Luhn algorithm, a formula developed in the 1950s to catch errors in long number sequences. Here is how it works: the payment system takes all the digits except the last one, doubles every second digit from right to left, subtracts 9 from any result over 9, adds all the results together, and then calculates what the last digit needs to be so the total is divisible by 10.
You do not need to calculate this yourself. The point is that the check digit is mathematically dependent on all the other digits. If you mistype even one digit, the check digit will not match, and the transaction will fail. This is why you can sometimes catch a typo when ready when entering your card number — the system rejects it before sending it to your bank.
The Luhn check is not a security feature in the sense that it does not prevent fraud. A fraudster who has your full card number can still use it. But it does prevent accidental errors and catches some automated fraud attempts that use randomly generated numbers.
What the digits do not tell you
The card number itself does not encode your name, address, expiration date, or CVV (the three-digit security code on the back). These details are stored separately in your bank's system and are not derived from the card number. Someone who knows your 16-digit card number cannot figure out your CVV or expiration date — they would need to see the physical card or access your bank's database.
The card number also does not tell you your credit limit, interest rate, or account balance. These are account details stored by your bank, not encoded in the plastic or the number itself. The number is straightforward an identifier that links a transaction to your account.
Why card networks standardized on different lengths
The variation in card length reflects the history of each payment network. American Express was founded in 1850 as a travel company and began issuing charge cards in 1958. It built its own infrastructure and chose 15 digits. Visa and Mastercard emerged later and adopted the 16-digit standard, which was recommended by the International Organization for Standardization (ISO). Discover, launched in 1986, also adopted 16 digits to match Mastercard.
The ISO standards allow for flexibility because the payment industry knew it would evolve. A 16-digit card can theoretically support billions of unique account numbers (the middle digits), which is more than enough for current use. The standards also allow for 13-digit and 19-digit cards to accommodate future growth or special use cases, though these are rare in consumer banking.
How to protect your card number
Your card number is sensitive information. If someone has your full 16-digit number, expiration date, and CVV, they can make online purchases without your permission. You should never share your card number in an email, text message, or over the phone unless you initiated the contact and you are certain you are speaking to your bank or a trusted merchant.
When you make a purchase online, look for a padlock icon in the address bar and make sure the URL starts with https (not http). This means the connection is encrypted. When you swipe or insert your card at a physical terminal, the merchant should not write down your number or take a photo of it. Modern terminals read the card electronically and do not need to see the number written down.
If your card is lost or stolen, call your bank when ready. Most banks have fraud protection that limits your liability to $50 if you report the loss quickly, and many waive the $50 entirely. The sooner you report it, the sooner your bank can block the card and issue a replacement.
Frequently Asked Questions
Why does my new card have a different number than my old one?
Each physical card gets a unique account number. When your bank reissues your card — whether because it expired, was damaged, or was replaced due to fraud — the new card has a new number. Your account itself stays the same, but the card number changes. This is why you need to update your card number with any merchants you have on file, such as subscription services or autopay bills.
Can someone use my card if they only know the first six digits?
No. The first six digits (the BIN) only identify your bank. A fraudster would need all 16 digits plus the expiration date and CVV to make a purchase. Knowing just the BIN tells someone which bank issued your card, but it does not let them use it. This is why it is safe to share your BIN if you need to verify your card issuer, but never share the full number.
Is the CVV the same as the last digit on my card?
No. The last digit of your card number is the check digit, which is part of the account number. The CVV (Card Verification Value) is a separate three-digit code printed on the back of your card (or the front, for American Express). The CVV is not encoded in the card number and is not used in the Luhn check. It is a security feature that proves you have the physical card.
Do all Visa cards have exactly 16 digits?
Most do, but not all. Visa cards can be 13, 16, or 19 digits according to the standard. The vast majority of Visa cards in circulation today are 16 digits. If you have a Visa card with a different length, it is likely an older card or one issued in a specific region, but it works the same way as a 16-digit card.
What happens if I enter my card number wrong?
The payment system will reject it before it reaches your bank. The Luhn algorithm check catches the error and returns a message saying the card number is invalid. You can then re-enter it correctly. This is a built-in safety feature that prevents typos from being processed as transactions.