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What Do Credit Card Numbers Mean?

What Do Credit Card Numbers Mean?
Alyssa Schwartz

Alyssa Schwartz

Updated November 20, 2021
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Editor’s note: Lantern by SoFi seeks to provide content that is objective, independent and accurate. Writers are separate from our business operation and do not receive direct compensation from advertisers or partners. Read more about our Editorial Guidelines and How We Make Money.
It’s a fact that anyone who has ever made an online purchase using a credit card likely knows all too well: credit cards have a lot of numbers. The credit card number itself can be as long as 19 digits — and those aren’t the only numbers that appear on a person’s card or that a consumer may be asked to provide when making a payment. Although it might seem like it to anyone who isn’t up on terminology about credit cards, those numbers aren’t random. Each credit card contains unique numbers that provide information about the credit card, offer security and fulfill other functions. Keep reading to learn what all those numbers on the back (and front) of a credit card actually mean. 

How Many Digits Are in a Credit Card Number?

A credit card number — the string of numbers that appear on the front of a card — can be as short as eight digits and as long as 19. Most cards land on the longer side, with 15 to 16 numbers on average. However, there is no defined length for credit card numbers.Whether long or short, the digits within a credit card number reveal some key information. For instance, they contain embedded information about the card itself, such as the brand of the credit card. 

The First Digit: Major Industry Identifier (MII)

Unless it’s a specialty card, the first digit in a credit card number often reflects the credit card network to which a card belongs. This typically holds true regardless of which bank issued the card.This means that knowing whether a card is a Visa or Mastercard, for example, can often come down to checking that first digit. In some cases, however, the first digit of a credit card may reflect the industry with which the card is affiliated, as you can see in the table below:

The First Six Digits: Issuer Identification Numbers (IIN)

The next five digits in a credit card number reveal information about the credit card issuer, such as a bank or credit union. Together with the first digit on a credit card, the first six digits together make up the Issuer Identification Number (IIN). This number indicates what type of credit card it is and where it was obtained. However, because a bank may have different products and brands, a person who looks at a number of credit cards from the same issuer may find that these numbers do indeed vary.

The 7-18 Digits: Account Numbers

While the digits that make up a credit card’s Issuer Identification Number would be the same for any cardholder who has the same type of credit card issued by the same financial institution, that’s not the case with the next group of numbers in the string. Starting with digit seven, the next numbers up until the final number are account identifiers that reflect the cardholder’s unique account. These numbers may or may not be the same as the credit card holder’s account number. If the two numbers are different, the cardholder should be able to find both when reading a credit card statement, even though only the account identifier would appear on the actual card. In the event that a credit card is lost or stolen, these numbers would be changed on the replacement card.

Why Do Card Number Lengths Vary?

Because there is no standard length for credit cards, the length of the account number will vary depending on the length of the entire credit card number. For a typical 16-digit credit card, the account number would consist of nine numbers, comprising digits seven through 15. Because American Express cards only contain 15 digits in the credit card number, the account numbers for those cards are only eight digits long. But if a credit card was, say, just 10 digits long, the account number would only consist of three numbers.

The Final Number: The Validator

The last digit in the string that comprises a credit card number is not part of the account number. Rather, it’s called the validator (and sometimes the checksum or check digit). While this digit doesn’t say much on its own, it functions as a secret check to ensure a credit card number is valid. The validator works by applying a mathematical formula, called the Luhn algorithm, to all of the digits in a credit card number. Once those numbers are plugged into the formula, the result would be the same as the validator number. If the number is not the same, it suggests that there is an inaccuracy, such as a typo in the credit card number provided or the transposal of two digits. This algorithm is often embedded in payment processors and not something a cardholder or merchant would check manually.

Numbers on the Back of Your Card

Now that we’ve covered the credit card number, what about all those digits on the back of the card? Here’s what they are and how they’re used.

Expiration Date

The credit card expiration date indicates when a credit card is valid until. This number may appear on either the front or back of the credit card. It consists of a month and a year, and a cardholder may continue to use their card until the last day of the month indicated.Although a credit card expiry date lets a person know when their card will need to be replaced, it also provides a security function. That’s because if someone is able to illegally obtain another person’s credit card number, they may not also have access to the card’s expiry date. Often when making a purchase, the requested credit card details will include that date. This may be in a four-digit (month and last two digits of the year) or six-digit (month and all four digits of the year) format. In such instances, if the purchaser is unable to provide both numbers, or enters the wrong expiry date, the authorization would fail. 

CVV

There’s another number on a credit card that is also used for security purposes, called the Card Verification Value or CVV. It’s sometimes called the security code. The CVV is a random number intended to reduce unauthorized credit card use. It is not the same as one’s security PIN. For most credit cards, this is a three-digit number that appears on the signature strip on the back of the card. American Express cardholders can find their four-digit CVV on the front of their credit card.Similar to the expiry date, a CVV is information that an unauthorized user would not have if they were able to access a credit card number on its own. If the CVV and credit card number do not match, a transaction (whether for a shopping spree or someone buying bitcoin with a credit card) should fail.

More Secure Technologies

While your various credit card numbers can provide some security, they’re not the only thing keeping your card secure. Traditionally, credit cards have what's called a magnetic stripe, or magstripe. This strip is typically located on the back of a card. When the card is swiped, its account number is transmitted to complete the purchase.However, as this technology has shown security flaws, credit card issuers have started to phase it out. Often cards will also have a smart chip, which is able to encrypt your information and generate a unique code for each transaction, making your information harder to steal. Rather than swiping your card with a chip (known as an EMV card), you'll dip it into a chip reader.Companies are also starting to look into biometric cards, which would use both a chip as well as an identifying feature, such as a fingerprint, to offer an extra layer of security.

Credit Card Number vs Account Number

With all this talk of numbers, you may be wondering: is there a difference between a credit card number and an account number? Many people think these are one in the same, but they aren’t. Whereas your credit card number appears on your physical card, your account number is on your credit card statement.If you need to replace your card because it is stolen or lost, you will get a new credit card number. Your account number, on the other hand, will remain the same.

Credit Card Number Tips

Although a credit card is a piece of plastic, the numbers embossed on it are sensitive financial details and should be carefully guarded. Here are some tips for keeping them secure.

Never Store Your Credit Card Number, Expiration Date and CVV in One Place

While each of these numbers on their own contain important details, in combination they give a malicious user everything they need to successfully process a transaction. Without also being able to enter the correct expiry date and CVV, they may not be able to complete their transaction.

Keep an Eye on Expiry Dates

While banks typically send out a new card in advance of the expiry date, there may be instances where a cardholder doesn’t receive their new card in time — and that can be stressful for anyone who relies on a credit card for everyday purchases. Keeping an eye on your credit card’s expiry date is a good way to avoid being caught without a working credit card.

The Takeaway

From picking a credit card to understanding what all the numbers on the front and back of the card mean, feeling comfortable paying with plastic can take some legwork. Depending on which credit card you get, your credit card numbers will vary. If you’re on the search for a credit card now that you know what all those little numbers mean, Lantern makes it easy to compare a credit card with another and figure out which one is right for you.
Photo credit: iStock/BartekSzewczyk
The tips provided on this website are of a general nature and do not take into account your specific objectives, financial situation, and needs. You should always consider their appropriateness given your own circumstances.SOLC1021238

About the Author

Alyssa Schwartz

Alyssa Schwartz

Alyssa Schwartz is an award-winning freelance writer whose work has appeared in The Globe and Mail, Vogue, Robb Report and other publications. Alyssa writes on a variety of finance topics for both individuals and small businesses.
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