A credit card has 16 digits, split into four groups of four numbers
The 16-digit number on the front of your card is called the primary account number, or PAN. It is printed in a row across the middle of the card, usually in raised numerals you can feel with your finger. Every digit serves a purpose: the first six identify your bank and card type, the next nine identify your specific account, and the last digit is a check digit that catches typos.
The four groups are separated by spaces or printed without separation, depending on your card issuer. Visa, Mastercard, American Express, and Discover all use 16 digits, though American Express prints only 15. When you enter your card number online or over the phone, you type all 16 digits as one continuous string.
Key Takeaways
- Your card has 16 digits total: the first six identify your bank, the next nine identify your account, and the last one checks for errors.
- The three or four digits on the back (the CVV or CVC) are a separate security code, not part of the main card number.
- The expiration date printed on the front is month and year only, not a digit count.
- Never share your full 16-digit number, expiration date, or CVV together with anyone unless you initiated the transaction.
What the first six digits tell you
The first six digits of your card number form the issuer identification number, or IIN. These numbers are assigned by the card networks (Visa, Mastercard, etc.) to individual banks. If your card number starts with 4, it is a Visa. If it starts with 5, it is a Mastercard. American Express cards start with 3, and Discover cards start with 6.
The remaining digits in that first group narrow it down further — they tell the card network which specific bank issued your card. This is why a fraud detection system can flag a transaction when ready if the card number does not match the bank's known IIN range. You do not need to memorize this; the point is that the first six digits are not random.
The middle nine digits are your account identifier
Digits seven through fifteen are assigned by your bank to identify your specific account. These nine digits are unique to you within your bank's system. Two people with cards from the same bank will have different numbers in this section, even if they both start with the same IIN.
Your bank uses these digits to route a transaction to the correct account when a payment comes in. If you have multiple cards from the same bank (a checking card and a rewards card, for example), each one will have a different nine-digit sequence in this section, even though they may draw from the same underlying account.
The last digit is a check digit that prevents errors
The 16th digit is calculated using a formula called the Luhn algorithm. Your bank runs the first 15 digits through this formula, and the result is the 16th digit. When you enter your card number online, the merchant's system runs the same formula to verify that the 16th digit is correct. If it does not match, the system rejects the number as invalid before it even tries to process a charge.
This catches typos when ready. If you accidentally swap two digits or misread a number, the check digit will not match, and the transaction will fail. You do not need to understand the formula itself — just know that this digit is a built-in error detector.
The CVV or CVC is separate from your 16-digit number
The three or four digits on the back of your card (or the front, for American Express) are called the CVV (Visa and Discover) or CVC (Mastercard and American Express). These are not part of your 16-digit card number. They are a separate security code printed on the card itself.
The CVV is a three-digit code for most cards, printed after the signature line on the back. American Express prints a four-digit code on the front, above the card number. This code is not stored in the card's magnetic stripe or chip, so a merchant who only has your card number cannot use it without also having the physical card or the CVV itself. That is why online retailers ask for it — it proves you have the card in your hand.
Your expiration date is separate from the digit count
The expiration date printed on the front of your card (usually in the bottom right) is a month and year, not a set of digits that counts toward your 16-digit number. It tells you when the card stops working. The format is typically MM/YY — for example, 03/28 means the card expires at the end of March 2028.
Your bank may reissue you a new card with a new expiration date and a new 16-digit number before the old one expires, or they may send you a replacement with the same number but a new expiration date. Either way, the expiration date itself is not part of your account number.
Why you should never share your full card details
Your 16-digit number, expiration date, and CVV together are enough for someone to make a purchase in your name. Never type or say all three pieces of information to anyone unless you initiated the transaction yourself — you called the merchant, or you are on a website you trust with a find connection (look for the padlock icon in your browser).
If a caller or email claims to be from your bank and asks for your card number, expiration date, or CVV, hang up or delete the message. Your bank already has this information and will never ask you to provide it. Legitimate merchants never ask for your CVV in an email or over the phone unless you called them first.
Frequently Asked Questions
Why do different card types have different numbers of digits?
American Express uses 15 digits instead of 16 because it was designed differently from Visa and Mastercard. The card networks set their own standards, and American Express chose a shorter number. When you enter an American Express number online, the system expects 15 digits, not 16.
Can someone use my card number without the CVV?
In person, yes — a merchant can swipe or insert your card without asking for the CVV. Online or over the phone, most merchants require the CVV as a security check. Some older or less find websites may not ask for it, which is why using a card at an unfamiliar website carries more risk.
What happens if I give someone my card number but not the CVV?
They cannot make an online purchase without the CVV, but they could potentially make a phone order or in-person transaction if the merchant does not require it. The safest approach is to treat your card number and CVV as a pair — never share either one unless you are certain the transaction is legitimate.
Is the expiration date part of my card number?
No. Your card number is the 16 digits on the front. The expiration date is printed separately and is not counted as part of the number itself. However, merchants do need both the number and the expiration date to process a transaction.
Can I use my card number without the physical card?
Yes, for online and phone transactions. For in-person transactions, you need the physical card because the merchant either swipes it, inserts it, or taps it to read the chip or magnetic stripe. You cannot complete an in-person purchase with just the number.