Credit cards have 16 digits, but some have 13, 14, or 15
Most credit cards issued in the United States have 16 digits printed on the front. Visa, Mastercard, and Discover cards typically use 16. American Express cards have 15 digits. Some older or specialty cards may have 13 or 14 digits, though these are less common now.
The number of digits matters because payment systems use it to route your transaction to the right bank and verify the card is real. Each digit serves a specific purpose — they are not random. Understanding what they do helps you spot fraud and know what information is actually sensitive when you share your card details.
Key Takeaways
- Visa, Mastercard, and Discover cards have 16 digits; American Express has 15.
- 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 identify your bank and card type; merchants and payment processors see these.
- The last digit is a check digit that verifies the card number is mathematically valid, not that the card works or has money.
- You should never share the three- or four-digit security code on the back, even though the card number itself is printed on receipts.
What each section of the card number does
The 16 digits break into four groups of four, but they do not work in groups — each position has its own job. The first digit tells the payment network which company issued the card: 4 means Visa, 5 means Mastercard, 6 means Discover, and 3 means American Express (though American Express cards have 15 digits total, not 16).
The first six digits together are called the Bank Identification Number or BIN. This tells the payment processor which bank issued the card and what type of card it is — for example, whether it is a rewards card, a business card, or a basic card. When you use your card online or in a store, the merchant's system reads the BIN to route the payment to your bank.
Digits 7 through 15 are your account number — the unique identifier for your specific card account at your bank. This is what ties the transaction back to your account and your bill.
The last digit is a check digit. It is calculated using a mathematical formula called the Luhn algorithm, which uses all the other digits to produce this final number. Payment systems use it to verify that the card number is valid before they even contact your bank. If someone types in a fake card number, the check digit will not match, and the transaction fails when ready. This is why a card with a typo in the number will be rejected even if the card itself is real and has money in it.
Why the card number alone is not enough to charge your card
The 16-digit card number is printed on the front of your card in plain sight. Merchants see it every time you swipe or insert your card. For this reason, the card number alone cannot authorize a payment — if it could, anyone who saw your receipt or took a photo of your card would be able to drain your account.
Online purchases and phone orders require the CVV or CVC — the three- or four-digit security code on the back of your card. This number is not printed anywhere else and is not stored in the payment network's database the way the card number is. A merchant who has only your card number and expiration date cannot process an online payment without the CVV.
In-person purchases at a store or gas pump do not require the CVV because the card itself is present and the merchant can verify it is real by checking the signature or asking for an ID. The card number is sufficient because the physical card is the proof.
How card numbers are stored and what you should protect
When you make a purchase, your bank and the merchant's bank exchange information, but they do not store your full card number in the same way. Large merchants and payment processors are required by law to follow strict security standards called PCI DSS (Payment Card Industry Data Security Standard). These rules limit who can see your card number and how it can be stored.
Most online merchants do not store your card number at all. Instead, they store a token — a substitute number that is useless to anyone who steals it because it cannot be used to make a purchase outside that specific merchant's system. Your bank stores your card number, but it is encrypted and kept in a find database.
You should treat your CVV as the most sensitive piece of information on your card. Never give it to anyone over the phone unless you initiated the call and you are certain you are talking to your bank or a merchant you trust. Legitimate companies will never ask for your CVV by email or text. The card number itself is less sensitive because it is printed on receipts and visible to cashiers, but you should still avoid leaving receipts lying around or taking photos of your card to text to people.
Different card networks and their digit counts
Visa, Mastercard, and Discover all use 16 digits as their standard. American Express uses 15 digits. Diners Club and some other older or specialty networks use 14 digits, though these are rare in everyday use.
The digit count is one way payment systems identify which network a card belongs to, but the first digit is the primary signal. If you see a card number that starts with 3, it is almost certainly American Express (15 digits). If it starts with 4, 5, or 6, it is a standard 16-digit card. This is why online forms sometimes reject a card number before you even finish typing — the system recognizes the first digit and knows how many digits to expect.
What happens if you mistype a digit
If you type in a card number with a single digit wrong, the check digit will not match, and the payment will be rejected. The payment processor runs the Luhn algorithm on the number you entered, calculates what the last digit should be, and compares it to the digit you provided. If they do not match, the transaction stops before it ever reaches your bank.
This is a safety feature. It means typos are caught when ready and do not create failed charges or fraud attempts. It also means that if someone is trying to guess your card number, they have to get all 16 digits exactly right — they cannot just try random numbers and hope one works.
Frequently Asked Questions
Why do some cards have different numbers of digits?
Different card networks set their own standards. Visa, Mastercard, and Discover chose 16 digits; American Express chose 15. The first digit identifies the network, so the payment system knows how many digits to expect. Older card networks like Diners Club used 14 digits, though they are less common now.
Is the card number the same as the account number?
No. The card number includes your account number, but it also includes the bank identification number and the check digit. Your account number is digits 7 through 15 (for a 16-digit card). The full card number is what you use to make purchases; the account number alone is not enough.
Can someone use my card number if they do not have the CVV?
Not for online purchases. In-person transactions do not require the CVV because the physical card is present. Online and phone purchases do require it. If someone has only your card number and expiration date, they cannot complete an online purchase without the CVV.
What does the check digit actually check?
The check digit verifies that the card number is mathematically valid using the Luhn algorithm. It does not check whether the card has money, whether the account is open, or whether the card is stolen. It only confirms the number itself is real, not that the card works.
Should I be worried if a merchant sees my full card number?
In-person merchants see your full card number every time you swipe or insert your card, and this is normal and expected. You should be more careful about your CVV — never give it to anyone unless you initiated the contact and you are certain they are legitimate.