A credit card has 16 digits, split into four groups of four
The 16 numbers on the front of your credit card are not random. Each digit or group of digits tells the card issuer, the merchant, and the payment network something specific about the card and the account behind it. Understanding what each section does helps you spot fraud, fill out online forms correctly, and know what information is actually sensitive.
The four sections are: the bank identification number (the first six digits), the account number (the next nine digits), and the check digit (the last digit). A separate three or four-digit code on the back, called the CVV or CVC, is not part of the 16-digit sequence but is equally important for online purchases.
Key Takeaways
- Credit cards have 16 digits printed on the front, arranged in four groups of four numbers each.
- The first six digits identify your bank and card type; the next nine identify your specific account; the last digit is a check digit that prevents typos.
- The three or four-digit code on the back (CVV or CVC) is separate from the 16 digits and required for online purchases.
- Never share your full card number, expiration date, or CVV with anyone except a merchant you trust, even if they claim to be from your bank.
The first six digits: bank and card type
The first digit tells you the card network. A 4 means Visa, a 5 means Mastercard, a 3 means American Express or Diners Club, and a 6 means Discover. This first digit is called the major industry identifier, and it narrows down which payment system processes the transaction.
Digits two through six together form the bank identification number, or BIN. This six-digit code identifies your specific bank or credit union. When you swipe or insert your card, the merchant's terminal reads the BIN first to route the transaction to the right processor. The BIN also tells fraud detection systems which bank issued the card, so they can flag suspicious activity faster.
The next nine digits: your account number
Digits seven through fifteen are your account number. This is the unique identifier for your specific credit account at that bank. No two cardholders at the same bank have the same account number. This is the part of your card number that ties the transaction back to your statement and your credit history.
Your account number stays the same for the life of the card, even if you request a replacement card for wear or damage. If your card is compromised and you get a new one, the bank issues you a new card number (all 16 digits change), but your underlying account number may stay the same in their system.
The last digit: the check digit
The sixteenth and final digit is called the check digit. It is calculated using a mathematical formula called the Luhn algorithm, which runs the first 15 digits through a specific set of operations. The result is a single digit that the payment system uses to verify that the card number was entered correctly.
If you mistype one digit when entering your card number online, the check digit will not match, and the transaction will be rejected before it even reaches your bank. This catches typos and prevents you from accidentally sending money to the wrong account. The check digit is not secret; it is printed right on your card for anyone to see.
The CVV or CVC: the three or four-digit code on the back
On the back of your card, usually in the signature strip area, is a three or four-digit security code. Visa and Mastercard call it the CVV (Card Verification Value). American Express calls it the CID (Card Identification Number) and prints it on the front. Discover calls it the CVC (Card Verification Code).
This code is not part of the 16-digit number, and it is not stored in the magnetic stripe or chip. It is printed on the card only, which means a merchant who has only your card number and expiration date cannot complete an online purchase without it. The CVV is the reason a thief who finds your card number alone cannot when ready use it to shop online.
Why the card number is sensitive but the check digit is not
Your full 16-digit card number, expiration date, and CVV together are enough for someone to make a purchase in your name. The check digit by itself is useless to a thief because it is derived from the other digits and is printed on every card. Knowing the check digit does not let someone reconstruct the account number.
The account number (digits 7–15) is more sensitive than the first six digits. Your BIN is semi-public; payment processors and fraud detection services maintain databases of BINs so they can identify card types and issuers. But your account number is private. If someone has your account number and expiration date, they can attempt to use it, even without the CVV, in some in-person or phone transactions.
What happens if your card number is compromised
If your card number is stolen, contact your bank or card issuer when ready. They will cancel the card and issue you a new one with a completely new 16-digit number. Your account number may or may not change depending on your bank's policy, but your card number will.
The new card will have a new expiration date and a new CVV. Any recurring charges you have set up (subscriptions, automatic bill pay) will need to be updated with the new card number. Your bank can usually provide a list of merchants you have authorized, so you know which ones to contact.
Frequently Asked Questions
Do all credit cards have 16 digits?
Most do, but not all. American Express cards have 15 digits instead of 16. Diners Club cards also have 14 or 15 digits depending on the card type. Visa, Mastercard, and Discover cards are consistently 16 digits. If you are entering a card number online and it rejects a 15-digit number, the form may not accept American Express.
Is it safe to give my card number over the phone?
Only to merchants you initiated contact with and trust. Never give your card number to someone who called you, even if they claim to be from your bank. Your bank will never ask for your full card number, expiration date, or CVV over the phone. If you are unsure, hang up and call the bank's official customer service number on the back of your card.
Can someone use my card number if they only have the first six digits?
No. The first six digits (the BIN) identify your bank and card type, but they do not identify your account. Millions of cardholders share the same BIN. Someone would need your full 16-digit number, expiration date, and CVV to make a purchase.
What does the expiration date have to do with the card number?
The expiration date is printed separately from the 16 digits, but it is required for online purchases along with the card number and CVV. The expiration date tells the merchant when the card will no longer be valid. When your card expires, the bank issues a new card with a new expiration date and new CVV, but your account number may remain the same.
Why does my replacement card have a different number if it is the same account?
For security. Each physical card is issued a unique 16-digit number. If your card is lost, stolen, or damaged, the bank cancels that specific card number and issues a new one. This prevents anyone who may have seen or recorded your old card number from using it after you report the problem.