A credit card has 16 digits, printed or embossed on the front

The long number on your credit card is called the Primary Account Number, or PAN. It is always 16 digits on Visa and Mastercard, though American Express uses 15 digits and some other card types use different lengths. These numbers are not random — they follow a specific pattern that identifies your bank, your account, and includes a built-in check digit that catches typos.

You will see this number printed twice on most cards: once in raised digits you can feel with your finger, and once printed flat below it. The raised version exists because older card readers used a mechanical imprint process. Today both versions serve the same purpose — they let you read the number whether you are paying online, over the phone, or in person.

The 16-digit number is what you need to give when you make a purchase. It is the most visible and most important number on your card, but it is not the only one.

Key Takeaways

  • Your credit card has 16 digits (15 for American Express) that make up your account number, and each digit serves a specific purpose in the banking system.
  • The first digit or two identify which bank issued your card; the next digits identify your specific account.
  • The last digit is a check digit that the payment system uses to verify you typed the number correctly.
  • Three additional numbers on the back (the CVV or CVC) are a security code separate from your account number and required for online purchases.
  • Your card also has an expiration date printed on the front, which tells merchants and payment systems when the card stops working.

What the first digits tell you

The first digit of your card number identifies the card network. Visa cards always start with 4, Mastercard with 5, American Express with 3, and Discover with 6. This single digit tells the payment system which company to route your transaction to.

The next few digits identify your specific bank or card issuer. Chase, Bank of America, Capital One, and every other bank that issues credit cards has its own code. So if your card starts with 4 (Visa) followed by 1 (Chase's code), the payment system knows immediately that this is a Chase Visa card before it even checks whether the account exists.

This is why you can sometimes guess what bank issued a card just by looking at the first few digits — they follow a published standard that payment processors use worldwide.

The middle digits are your account number

After the network and issuer codes, the remaining digits (minus the last one) make up your unique account number. This is the part that distinguishes your card from every other Chase Visa card in existence. Two people could have Chase Visa cards that start with the same digits, but the middle section will always be different.

The bank uses this section to look up your account when a transaction comes through. It connects the card number to your name, address, credit limit, and payment history. Without this section, the payment system would have no way to know whose account to charge.

The last digit is a check digit

The final digit on your card is called a check digit. It is calculated using a mathematical formula called the Luhn algorithm, which uses all the other digits to produce this one number. The purpose is to catch typos.

When you enter your card number online or over the phone, the payment system runs the same formula on the first 15 digits. If the result matches the 16th digit you entered, the system knows you typed it correctly (or at least that you typed a valid card number format). If it does not match, the system rejects the transaction immediately without even contacting your bank.

This catches most accidental mistakes before they waste time or money. It does not prevent fraud — a criminal who types a card number intentionally will get the check digit right — but it does prevent honest typos from going through.

The three-digit security code on the back

On the back of your card, usually in the signature strip area, you will find three digits printed to the right of the signature line. This is called the CVV (Card Verification Value) on Visa and Mastercard, or CVC (Card Verification Code) on American Express. Discover calls it the CID.

This code is separate from your 16-digit account number. It is not stored in the magnetic stripe or the chip on your card — it is printed only on the physical card itself. This means a merchant who has your card number from a previous transaction cannot process a new purchase without the CVV, because they would need the physical card to read it.

Online merchants are required to ask for this code for card-not-present transactions (when you cannot hand them the card). It is one of the main reasons why stolen card numbers alone are not enough to make unauthorized purchases online.

The expiration date and what it controls

Your card has a month and year printed on the front, usually in the lower right. This is your expiration date. The card stops working on the last day of that month, even if you have not reached your credit limit and your account is in good standing.

Banks issue new cards before the old one expires, usually 30 to 60 days before. The new card will have a different 16-digit number, a new expiration date, and a new CVV code. You will need to update any recurring payments (subscriptions, automatic bill pay) with the new number.

The expiration date exists partly for security — it limits how long a stolen card number remains useful — and partly for logistics. Banks use the expiration date to know when to send you a replacement card and to flag old numbers in their system.

Why card numbers are different lengths on different networks

Visa and Mastercard settled on 16 digits decades ago and have kept that standard. American Express chose 15 digits and has never changed. Discover also uses 16. Some specialty cards or international cards may use different lengths.

The length does not matter for security or function — it is simply a choice each network made early on. The Luhn check digit works the same way regardless of length. The important thing is that when you enter your card number, you enter all the digits exactly as they appear on your card, because the payment system expects a specific length for each network.

Frequently Asked Questions

Is it safe to write down my credit card number?

Writing down your full 16-digit number plus CVV is risky because anyone who finds the paper has everything needed to make online purchases. If you must write it down, store it in a locked place and never include the CVV. Better options: save the card in your phone's secure wallet, use your bank's app, or memorize the number if you use it often.

Do all credit cards have 16 numbers?

Visa and Mastercard always have 16 digits. American Express has 15. Discover has 16. Some debit cards, store cards, and international cards may differ. Check your specific card — the number of digits should match what your bank told you when you received it.

Can someone use my card if they only have the 16-digit number?

Online, no — they would also need the CVV code from the back. In person or over the phone at an older merchant, possibly, though most modern systems now require CVV for all transactions. The 16 digits alone are not enough for most current payment methods, which is why the three-digit code exists.

What happens if I type my card number wrong?

If you get any digit wrong, the check digit will not match and the payment system will reject it before sending it to your bank. You will see an error message asking you to re-enter the number. This is the Luhn algorithm working — it catches typos automatically.

Why do I need to enter my expiration date if the card number already identifies my account?

The expiration date is a second verification step. It confirms that you have the physical card in your hand (or at least that you have seen it recently), because the expiration date changes every few years. It also prevents old stolen card numbers from being used after the card has been replaced.