How to Tell a Card’s Type From Its Number

Credit and debit card numbers serve as unique identifiers for financial transactions, facilitating purchases and payments. Understanding the structure of these numbers can be useful for consumers, particularly when completing online forms that often require specific card type recognition. This knowledge helps ensure accurate data entry and a smoother transaction process.

The Anatomy of a Card Number

A payment card number is not a random sequence but rather a structured series of digits, typically ranging from 13 to 19 digits long. This sequence is composed of three main components, each serving a distinct purpose in identifying the card and its associated account.

The initial four to eight digits form the Issuer Identification Number (IIN) or Bank Identification Number (BIN). These digits identify the card’s issuing financial institution and the major payment network, such as Visa or Mastercard. This portion helps determine the card’s type, as different networks are assigned specific starting digit ranges.

Following the IIN/BIN is the individual account number, which identifies the cardholder’s account. This segment can vary in length, ranging from 6 to 12 digits. The final digit of the entire card number is a check digit, used for mathematical validation.

Key Starting Digits and Card Networks

The first digit of a card number, known as the Major Industry Identifier (MII), identifies the major card network. For instance, Visa cards consistently begin with the digit 4.

Mastercard numbers start with the digit 5, though some newer cards may begin with 2. American Express cards start with either 34 or 37. Discover cards commence with the digit 6.

Diners Club cards start with 300-305, 309, 36, 38, or 39. JCB cards begin with the range 3528-3589. Most cards are 16 digits, but American Express cards are 15 digits, and Diners Club cards are 14 digits. Some card types can be up to 19 digits.

Validating Card Numbers with the Luhn Algorithm

The Luhn algorithm, also known as the “mod 10” algorithm, is a checksum formula applied to payment card numbers. Its purpose is to validate the mathematical integrity of the card number, helping to detect input errors. This algorithm does not confirm whether a card is active, valid, or real, but rather checks if the number follows a specific mathematical pattern.

The process involves doubling every second digit of the card number, starting from the rightmost digit (excluding the check digit). If doubling a digit results in a two-digit number, its individual digits are then added together. All the resulting single-digit numbers, along with the unchanged digits, are summed. If the total sum is a multiple of 10, the card number is considered mathematically valid according to the Luhn algorithm.

What Card Numbers Cannot Tell You

While a card number can reveal its network and issuer, it does not provide full information about the card’s status or the cardholder. For instance, the number alone cannot tell you if the card is currently active, has expired, or has been canceled. A card number might pass the Luhn algorithm check, but still belong to a non-existent or invalid account.

A card number does not contain personal identifying information about the cardholder, such as their name, address, or contact details. Financial specifics like the card’s current balance, available credit limit, or transaction history cannot be determined solely from the card number. These details are maintained by the issuing bank. Protecting your full card number, along with the expiration date and security code, remains important for safeguarding your financial information.