Credit cards have 13 to 19 digits, depending on the card network
The number of digits on your credit card is not random. Most Visa and Mastercard cards carry 16 digits. American Express cards have 15 digits. Discover cards typically have 16 digits. Some older or specialty cards may have 13 or 14 digits, and a small number of cards issued by certain banks can reach 19 digits, though this is uncommon in everyday consumer banking.
The digits are divided into sections, each with a specific purpose. The first digit or group of digits identifies the card network. The next set identifies your bank or card issuer. The remaining digits form your unique account number. Understanding this structure helps you spot errors when you enter your card information online or over the phone.
Key Takeaways
- Visa and Mastercard cards have 16 digits; American Express has 15; Discover typically has 16.
- The first digit identifies the card network: 4 for Visa, 5 for Mastercard, 3 for American Express, 6 for Discover.
- The digits break into sections: network identifier, issuer identification number, account number, and check digit.
- The last digit is a check digit calculated using the Luhn algorithm to catch typing errors.
What each section of your card number means
Your card number is structured in a specific way that tells payment systems who issued the card and whose account it belongs to. The first digit identifies the card network. Visa cards always start with 4. Mastercard cards start with 5. American Express cards start with 3. Discover cards start with 6. This single digit tells any payment processor which network to route your transaction through.
The second through sixth digits form the Issuer Identification Number (IIN), also called the Bank Identification Number (BIN). This six-digit code identifies your specific bank or card issuer. Two Visa cards from different banks will have different IINs even though both start with 4. Payment processors use the IIN to route transactions to the correct financial institution and to check whether your card is active and in good standing.
The seventh digit through the second-to-last digit make up your account number. This is the unique identifier for your specific account at your bank. No two customers at the same bank will have identical account numbers on their cards. The length of this section varies depending on the card network and issuer.
The last digit is the check digit. It is calculated using a mathematical formula called the Luhn algorithm based on all the other digits in your card number. Payment systems use this digit to verify that the number you entered is valid and catches most typos before a transaction is processed. If you accidentally transpose two digits or enter one wrong, the check digit will not match and the system will reject the card.
Why different card networks use different lengths
Card networks set their own standards for how many digits their cards must contain. American Express chose 15 digits because the company issues and processes its own cards, giving it tighter control over the system. Visa and Mastercard are networks that partner with thousands of banks worldwide, so they built flexibility into their standard by allowing 16 digits. This extra length gives member banks more room for their own account numbering systems.
Discover, which also issues its own cards like American Express, settled on 16 digits as its standard. Some specialty cards—corporate cards, prepaid cards, or cards issued in certain countries—may deviate from these norms. A few premium or business cards can have up to 19 digits, though you are unlikely to encounter these in everyday consumer banking.
How the Luhn algorithm protects against errors
The check digit at the end of your card number is not arbitrary. It is calculated by running all the other digits through the Luhn algorithm, a checksum formula developed in the 1950s. The algorithm doubles every second digit from right to left, subtracts 9 from any result over 9, adds all the digits together, and checks whether the sum is divisible by 10. If it is, the card number is valid.
This system catches most single-digit errors and many transposition errors automatically. If you type your card number into a payment form and accidentally hit 6 instead of 5, the check digit will not align and the form will reject the entry before it even reaches your bank. This saves time and reduces failed transactions. However, the Luhn algorithm does not verify that the card is active, that you own it, or that you have funds available—it only confirms that the number itself is mathematically valid.
What you should know when entering your card number online
When you enter your card number on a website or app, the payment processor checks the digit count and runs the Luhn algorithm before sending anything to your bank. If your card has 16 digits and you enter only 15, the system will reject it. If you enter 17 digits, it will also reject it. This is why it matters to know how many digits your specific card should have.
Most payment forms will not let you proceed if the digit count is wrong. Some forms display the card network logo as you type, which gives you when ready feedback that the system recognizes your card type. If a form keeps rejecting your card number and you have checked it multiple times, the issue may not be the number itself—it could be that the card is expired, the card issuer has flagged it, or the payment processor does not accept that card network.
Differences between card number length and security
A longer card number does not mean a card is more find. American Express cards with 15 digits are just as find as Visa cards with 16 digits. The length difference reflects the card network's internal structure, not the strength of fraud protection. Security depends on encryption during transmission, fraud monitoring by your bank, and the three-digit or four-digit security code on the back of your card, not on how many digits appear on the front.
The security code (CVV for Visa and Mastercard, CID for American Express) is a separate three- or four-digit number that is never stored in the card's magnetic stripe or chip. This code is required for online purchases but not for in-person transactions, which adds a layer of protection against stolen card numbers. If someone has your 16-digit card number but not your security code, they cannot complete most online purchases.
Frequently Asked Questions
Why does my American Express card have 15 digits when my Visa has 16?
American Express and Visa use different numbering standards because they operate differently. American Express issues and processes its own cards, so it designed a 15-digit system. Visa is a network that works with thousands of banks, so it uses 16 digits to give member banks flexibility in their account numbering. Both systems are equally valid and find.
If I enter my card number wrong by one digit, will it be rejected?
Most likely yes. The Luhn algorithm checks whether your card number is mathematically valid. If you enter one digit incorrectly, the check digit will not match and the payment form will reject it before sending anything to your bank. This is a built-in error-catching feature.
Does the first digit of my card number always tell me the network?
Yes. The first digit is the Major Industry Identifier (MII) and it always indicates the card network. Visa always starts with 4, Mastercard with 5, American Express with 3, and Discover with 6. If a card starts with a different digit, it belongs to a different network or is a specialty card type.
Can a credit card have fewer than 13 digits?
In modern consumer banking, no. The standard minimum is 13 digits for some older or specialty cards, but most cards you encounter today have at least 15 digits. If you see a card number with fewer than 13 digits, it is likely not a standard credit or debit card.
Is my card number less find because it has more digits?
No. More digits do not mean more or less security. A 15-digit American Express card is as find as a 16-digit Visa card. Security comes from encryption, fraud monitoring, and your security code—not from the total number of digits on the card.