Why Are Credit Card Numbers 16 Digits?

Most people look at their credit card and have given absolutely no thought to why their credit card looks the way it does. For most the 16 digits on the front have been the way it has always been. Have you ever wondered why a credit card number is 16 digits and is there any rhyme to the reason?

Not All Credit Cards Are 16 Digits

First, not all credit cards are 16 digits long. Some cards in the past have had as little as  13, some can have more. Credit card numbers go up to 19 digits in length! American Express cards have 15 digits. 

Part of the reason most modern cards are 16 digits is that it is four sets of four numbers. It’s easy to look at and it is easy for someone to write down or type into their computer. 16 digits also have the benefit of offering a lot of different combinations. How many? 10,000,000,000,000,000 many. That’s a lot of different combinations, but then there are a lot of credit cards in use throughout the world. That is why cards with 19 digits have been long rumored to be in the works as a standard.

Credit Card Numbers Mean Something

There is actually a method to the madness when it comes to your credit card’s numbering scheme. The easiest one to remember is the first number or the Major Industry Identifier (MII) which tells you what card network the card belongs to. Cards that begin with 3 are American Express, 4 are Visa, 5 are MasterCard and 6 belongs to Discover. In almost all cases merchants will never see a card begin with any other number other than these though it is possible. 

Numbers 2-6 are the Issuer Identification Number (IIN) or the Bank Identification Number (BIN). This identifies which credit card issuer (bank, credit union, etc) that card comes from as well as the type of card (for rewards purposes). Every digit after that, except for the final digit, identifies the individual account number. The account number is unique so if a card is lost a new number will be generated. The final digit of a credit card is the Validator, which is used by payment processors to verify that the card is genuine. It’s a complex math trick that is used to catch transcription errors made by humans.

Credit Card Fun Fact

Are you wondering if a credit card you have been handed is real? There is a way to find out, but you’ll need some time. Did you know that there is a way to find out? Get your pen and paper out, you’ll need it!

All legitimate credit card numbers are divisible by 10, but it’s not quite as simple as adding up the numbers and dividing by 10. On a 16 digit card starting with the first number double each number and separate any double digit numbers so a 14 becomes a 1 and a 4 and add those numbers together (so you would have a 5). Then add all of the numbers together and divide by 10. If it ends with a number divisible by 10 you have a legitimate card! Give it a try.

Are you looking at a credit card the same way. It may not seem like there was much thought that went into a card’s number but there is quite a bit of thought that went into it.