# How to Tell if a Credit Card Is Fake in Under 60 Seconds

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## eHow Money Blog

A little-known fact is that every single credit card number conforms to something called the Luhn algorithm.

We can’t believe your credit card never told you about Luhn either.

Your credit card has a secret-aside from the 40 bucks you racked up on Ventis this week.

A little-known fact about these ubiquitous pieces of plastic is that every single credit card number conforms to something called the Luhn algorithm.

What’s that? Basically, it’s a formula you can use to check any credit card number. Also, we’re pretty sure there’s a neat party trick in there somewhere.

Here’s how it goes. Using your own card, or the card below, try the following:

• Starting with the second-to-last digit of the credit card number (in the example above, a 7), double every other digit on the card number. For the card above, your numbers would be as follows: 8 5 14 8 8 5 12 2 10 6 8 3 18 1 14 3.
• Take any double-digit numbers you have and add each digit to make it a single digit (that means 14, 12, 10, 18 and 14 in our example). So your numbers are now: 8 5 5 8 8 5 3 2 1 6 8 3 9 1 5 3
• Add up all of these single digits (8 plus 5 plus 5 plus 8, etc.).

Is the sum for your card divisible by 10? All credit, debit and bank card numbers are. That’s why it’s also called a “Mod 10 check.” If it isn’t divisible by 10, you either miscalculated (understandable), or you somehow got your hands on a fake, like this one. (Sorry, did the “Your Credit Card” part ruin the surprise?)

Now go tell your friends you’re psychic/a genius and wow them with this little trick.

How Do We Know All This? Cuz we’re brilliant. Also:
The ISO knows what’s up-they call the shots.
Hey, another fake credit card number. What are the chances?

-Ariel Dreyer, Serious Coin Contributor

Photo credit: Robert Llewellyn/Workbook Stock/Getty Images and Aaron Foster/Photographer’s Choice/Getty Images

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