# Test Credit Card Numbers With Luhn Credit Card Validation

Published 7/11/08 (Modified 6/17/11)

By MoneyBlueBook

**What Do the Credit Card Numbers Mean, and How Are Valid Credit Card Accounts Generated?**

Have you ever wondered how credit card companies generate all those account numbers that appear on the face of the credit cards you carry around in your wallet? At first glance the numbers, while neatly arranged, appear to be completely random. But would it surprise you to know that there is indeed meaning and actual mathematical methodology to the way the numbers are sequenced? The process of generating real credit card numbers and validating them based on a proven mathematical formula is not only intriguing on an intellectual level and a hacker's dream, the carefully calculated way the numbers are ordered is actually quite beautiful and elegant when you come to understand how it works.

Before I get down to explaining the anatomy of credit card numbers and discussing how credit card numbers are generated, I think it's prudent to remind everyone the intent of this article. The goal of this blog post is not to encourage or get people thinking about how to go out and create fake credit card numbers on their own for improper means. The purpose is to shed some light on the science behind the mathematical sequencing technology of valid credit card numbers and offer some insight into something that many of us frequently see and use everyday, but oftentimes don't pay much attention to.

Please take in the information provided for purely academic and entertainment reasons. I'm not trying to encourage anyone to create fake credit card numbers and get themselves in trouble with the law. For anyone even thinking about engaging in fake credit card number hacking, keep this in mind - using mathematically generated credit card numbers to purchase products over the Internet or in real life is not only unethical and highly illegal, it's also not yet technologically possible (yet), based on the sheer probability of long shot odds of 1 in trillions. After reading everything I'm about to say carefully, you'll also realize that there is no realistic way to generate actual working credit card numbers that could be used for anything but entertainment reasons. The math and science behind generating authentic credit card numbers are only good for validation purposes and not sufficient for creating workable numbers as several highly encrypted numerical components are still needed. So, with that obligatory disclaimer out of the way, here is a short guide on how anyone can generate and verify the authenticity of any credit card number.

**Basic Background About Credit Card Numbers and How They Work **

Rather than ask you to take out a credit card out of your wallet to examine it, I've provided a picture of a prototypical card - in this case, it's a Visa credit card. While different card types offer different lengths of numerical digits, most major credit card issuers popular in the United States have 16 primary numbers on the front face of the card. Visa, MasterCard, and Discover cards all have 16 digits. American Express is the only major credit card issuer in the U.S. with one less number - at 15 digits. Regardless of the length of numbers, their numerical sequencing is still guided by the same Luhn validation formula, the mathematical check sum equation that makes all valid credit card numbers error free.

As you can see from the picture of the Visa card above, the very first 6 credit card number sequence is known as the issuer identification number (IIN) or bank identification number (BIN). These first 6 numerical digits denote the credit card network and the banking institution the card is a member of. The issuer identifier number also incorporates the card type's special identifying numerical prefix.

- All typical 16 digit Visa account credit card numbers start with a prefix of 4.
- All 16 digit MasterCard account numbers start with a prefix of 5.
- All 16 digit Discover account numbers start with a prefix of 6011.
- All 15 digit American Express credit card numbers start with a prefix of 37.

There is less randomization during this initial set of 6 digits as the numbers are determined purely by the card issuing source. Validation systems that want to go the extra mile in verifying authenticity oftentimes scan this first numerical sequence to match the known bank and issuing location of the card with the provided customer billing address for further validation accuracy.

The lone digit at the very right end of the complete 15 or 16 digit credit card number sequence is known as the "check digit", which often is the final number that is computer generated to satisfy the mathematical formulations of the Luhn check sum process. Meanwhile, in between the first 6 digits and the last single check digit is the actual personalized account number - the 8 or 9 digit sequence given by the card issuer. For more basic background information about credit card numbers, check out this credit card features **brochure** for more useful knowledge about the embossed and printed information found on your typical plastic credit card.

**What's The Secret Behind The Luhn Algorithm, Also Known As The "Modulus 10" Or "Mod-10" Formula?**

The Luhn Algorithm is the check sum formula used by payment verification systems and mathematicians to verify the sequential integrity of real credit card numbers. It's used to help bring order to seemingly random numbers and used to prevent erroneous credit card numbers from being cleared for use. The Luhn Algorithm is not used for straight credit card number generation from scratch, but rather utilized as a simple computational way to distinguish valid credit card numbers from random collections of numbers put together. The validation formula also works with most debit cards as well.

The Luhn formula was created and filed as a patent (now freely in the public domain) in 1954 by Hans Peter Luhn of IBM to detect numerical errors found in pre-existing and newly generated identification numbers. Since then, it's primary use has been in the area of check sum validation, made popular with its use to verify the validity of important sequences such as credit card numbers. Currently, almost all credit card numbers issued today are generated and verified using the Luhn Algorithm or Modulus, Mod-10 Formula. Needless to say, if you come upon some existing credit card numbers that fail the Luhn algorithm when put to the test, it is safe to assume that they are not valid or genuine numbers.

The one thing to keep in mind is that validity in terms of passing the Luhn test only means that it is mathematically valid for computational compliance purposes. It does not guarantee that the credit card number sequence is indeed a working number that is backed up with a valid credit card account on the card issuer's end. It is not unremarkable for one to artificially generate a mathematically valid credit card number that passes the Luhn validation check, but still ultimately fails as a fake credit card number with no actual substance. The Luhn algorithm only validates the 15-16 digit credit card number and not the other critical components of a genuine working credit card account such as the expiration date and the commonly used Card Verification Value (**CVV**) and Card Verification Code (CVC) numbers (used to prove physical possession of the debit or credit card).

**The Nerdy Process Of Applying The Luhn Algorithm To The Creation and Validation Of Credit Card Number Sequences**

For those who hate math or get scared when they encounter a bunch of scary looking mathematical formulas and numerically inspired descriptions, you are not alone. I personally hate math as an academic subject and was rather terrible at it back in high school and college, but if you like visual, thinking puzzles like Sudoku, you'll like working with the Luhn Algorithm. It's pretty clever and remarkably well put together. It's also pretty easy to explain.

- First, you'll need to lay out all 15 or 16 numerical digits of the credit or debit card number. The Luhn Algorithm always starts from right to left, beginning with the rightmost digit on the credit card face (the check digit). Starting with the check digit and moving left, double the value of every alternate digit. Non-doubled digits will remain the same. Remember that the check digit is never doubled. For example, if the credit card is a 16 digit Visa card, the check digit would be the rightmost 16th digit. Thus you would double the value of the 15th, 13th, 11th, 9th digits, and so on until all odd digits have been doubled. The even digits would be left the same.
- For any digit that becomes a two digit number of 10 or more when doubled, add the two digits together. For example, the digit 5 when doubled will become 10, which turns into a 1 (when 1 and 0 are added together). Likewise, the digit 9 when doubled will become 18, which becomes 9 (as 1 and 8 are added together). Obviously, 0 when doubled will remain 0.
- Now, lay out the new sequence of numbers. The new doubled digits will replace the old digits. Non-doubled digits will remain the same. Thus, you should be able to come up with a new sequence of 15 or 16 numerical digits depending on card type.
- Add up the new sequence of numbers together to get a sum total. If the combined tally is perfectly divisible by ten (ends in 0, like 60 for example), then the account number is mathematically valid according to the Luhn formula. If not, the credit card number provided is not valid and thus fake or improperly generated.

**An Example Of the Luhn Validation Technique In Action - Using Homemade Graphics **

For the visual types like myself, let's use the American Express credit card on the right to better demonstrate the doubling and addition mathematics of the Luhn Algorithm. Follow the numbers and you'll realize that it's not as difficult as it may first appear. It's actually very easy once you get the hang of it. You won't look at credit card numbers the same way ever again after you get a good grip of it - I assure you. You'll find yourself testing credit card numbers for fun!

Ignoring the obvious Amex logo on the card, right of the bat it's clear the account number is that of an American Express number - denoted by the numerical prefix - "37". Now let's crunch the numbers through the Luhn Algorithm using the following displayed Amex credit card number: 3759-876543-21001. It doesn't matter if the credit card number sequence has 15 numbers like the American Express or 16 numbers like Visa, MasterCard, or Discover, the Luhn validation check should be able to verify whether this card number is a mathematically authentic credit card number regardless. Follow the Luhn steps from #1 to #4 below, starting with the rightmost check digit.

In this case, the total calculated sum was 57, which is not divisible by 10 (the added up sum does not end with zero). Thus the number fails the Luhn Algorithm validation check. According to the Luhn test, this particular Amex credit card number is completely bogus and fake. The numbers were likely randomly slapped together. To make this particular set of numbers Luhn compliant and error free, all we would have to do is change the all important "check digit" number from 1 to a 4, which would result in a total sum of 60, thereby becoming Luhn compliant.

If you want to test this mathematical theory out in real life, I recommend pulling out your own credit cards and spending a few seconds to run a quick Luhn screening on them just for your own amusement and education. Pretty neat isn't it? If you want another credit card number to test on, try using the credit card number that is displayed on the cartoon "VIZA Card" [sic] that Bart Simpson is holding up in the graphic at the top right of this article - the card is in the name of "Rod Flanders", and the credit card number is: 8525-4941-2525-4158. Tip: Just by looking at the prefix numbers you probably should already be able to tell that the account number's completely random and fake.

**Use The Luhn Formula To Validate Existing Accounts But Don't Attempt To Create and Use Fake Credit Card Numbers **

Now with this new found knowledge, keep in mind you still won't be able to randomly generate genuine workable credit card numbers. The Luhn theory only allows you to generate mathematically compliant credit card test numbers, not hack workable ones. Besides, without valid expiration dates, and valid CVV2, CVC2, or CID numbers (the special security codes printed on the back or front of credit cards as additional authentication measures), you still wouldn't be able to legitimately use your self generated numbers to run credit transactions anyway.

Cracking and hacking the security codes found on credit cards is currently impossible. To calculate a workable 3 digit CVV2 security code, the algorithm requires a primary account number (PAN), the 4 digit expiration date, a special 3 digit service code, and a pair of DES keys. With such heavy encryption and billions to trillions of numerical possibilities, unless you have God-like mental processing power and a fleet of super computers at your disposal, you won't be able to use brute force guessing attempts to crack the codes.

While it's good to use this type of information to education yourself on the inner workings of credit cards and mathematical validation theory, it's best to stay away from trying to further crack the secret of credit card codes to come up with free workable account numbers. Don't use the Luhn Algorithm for anything else but personal entertainment and amusement.���� Please don't go around trying to generate a list of fake credit card numbers on your own and trying to buy stuff with them. I know some of you out there may be tempted to try, but you'll just get yourself in trouble.

October 7, 2010 at 5:53 pmWow. I am amazed at some of these posts! They can't be serious! Anyway, I was hoping to be able to find out how to tell if a card is a bank card or a P card a Debt card an so on.

October 10, 2010 at 1:57 amSeriously. Get a life everybody.

Tried this nifty thing with my visa and it worked, but my american express didn't. checked my math and everything...

October 10, 2010 at 9:39 amPlease i need just one valid visa credit card with full details and i will be very greatful to whomever helps me with one and i will reward that person with good.

Thanks and best regards

October 10, 2010 at 4:08 pmit's around 4am here in our beautiful country, i should be sleeping between my 2 beautiful kids, but all the stupid people asking for complete credit card information have driven me laughin' crazy! Raymond's intention of writing this blog was really great. I was asked by my mother to create a Paypal account for her using her CC, but it was denied, maybe because of incorrect mailing address (as we transferred from the city down to province). I thought this article would help me have my mom's cc validated, but i found out that this article is more helpful than i thought (though mommy's cc wasn't validated at all). And this article just became so much interesting upon reading all the crazy comments written by those effin' soy nuts!

To all the desperate freakin' fools out there, GO TO THE BANK NEAREST YOU AND PERSONALLY APPLY FOR A CREDIT CARD!

OH AND FYI! THE FBI PEOPLE WILL FLY ALL THE WAY FROM THE U.S. TO YOUR COUNTRY JUST TO HAVE YOU NAILED BEHIND BARS! NICE TRY PEEPZ!

RAYMOND, excellent article you have here buddy :)

October 15, 2010 at 8:56 pmI just wanna know how to get a credit card or create a credit card account online.

October 16, 2010 at 5:46 pmGuts for you cuppycake!!! The FBI would not be able to fly to another country to arrest someone. They wouldn't get past customs because of Jurisdiction rights. They will have none in any other country. That's why criminals in car chases( in USA) head for the border because the police cannot follow them there(to Mexico or something). If anyone could have jurisdiction to arrest in a country they are not from is Interpol because they cover international laws. If the FBI try to make an arrest in another country they themselves will get arrested by the Local police. HAHAHA. And to those dummies wanting credit card numbers. YOU WILL NEVER FIND ONE LEGALLY!!! NOONE WILL BE STUPID ENOUGH TO GIVE OUT THEIR OWN CREDIT CARD INFO TO RANDOM PEOPLE!!!!!!!!!!!!!!!!!!!

October 20, 2010 at 11:42 amI need a valid Visa card number with CVV2 and expiration date.

October 21, 2010 at 10:18 pmi want to know if there is a difference between debit cards and credit cards. and if there is, could you say what it is?

October 21, 2010 at 10:20 pmyour answer would be extremely appreciated (for a project I'm working on).

November 9, 2010 at 6:05 amI just came across your bloq today and i read about the Luhn Formula and was interested. I think I understand the basics behind it. I was wondering if the formula is the same for Mobile airtime prepaid vouchers? Your post was very educative to me as I am computer engineering student and I do programming quite a lot with C++ and Java.

I kept laughing while going through the posts on the blog: from people begging you to those threatening to end their lives! Some people are sick. I couldn't help noting that if you obliged their requests and gave them your own credit card numbers, you'd be bankrupt within one hour! I know statistics don't lie but I didn't like the statistics about Africa originating 75% of all the inappropriate posts. Who are these bastards giving Africa a bad name?

I am from Kenya and I know that it is really stupid to expect someone to give a total stranger credit info or to generate a credit card number that really works (that means with a valid name, verification code and expiry date). It can be possible - just like it is possible to be struck by lightning and yet billions of people go through their entire lifetime without ever getting to be struck. Honestly, the time and energy required to hack into the credit card technology would be better spent getting a degree, securing a job and applying for a legit credit card! The sooner people realize that in the their lives, the better for them. And the better for us all!

Thanks for educating me on the Luhn Formula. I will try to code a simple program for checking if a sample card number is compliant to the formula. it should be really simple.

November 9, 2010 at 6:14 amSomeone asked for the difference between Credit cards and Debit cards. I am not an expert but I can give my take on the issue.

A Debit card is a card issued by a bank or agency with which you have deposits. The card allows you to withdraw cash or buy items ONLY with the money that you already have in your account. Of course banks can arrange overdrafts for you, which you will pay interest for but the basic fact is that you spend what you already have.

A Credit card, as the name, suggests allows you to spend on credit. You are allowed to withdraw cash at ATM or buy items with money that you have borrowed from the issuing agency. At the end of the month or three months etc, you get a statement indicating all the money you spent on your credit card and you have to refund the agency - with interest, of course.

Raymond, correct me if I am wrong. I would appreciate additional information especially on the credit card.

I have a Debit Card and I know about that!

November 20, 2010 at 4:26 pmthis really opened my mind again, i knew it once but forgot it, there's just one thing i need to ask you, could you give me a few valid visa numbers, fake of course, not from real cards, i'd like to examine them because i doon't think i entirely understand it and that would really help me, thank you.

many thanks for placing this.

December 8, 2010 at 7:47 pmWhat machine do company's use to imprint the credit card numbers on the card?

December 13, 2010 at 5:40 amThank you for the article about credit card numbers. I thought it was quite interesting. Amusingly, my debit card validates as a credit card number... anyways.

have a great day!

December 15, 2010 at 8:11 pmCould someone give me a valid Visa card number along with a expiration date and Security Code? Not a card that someone actually uses in ever day life of course.. I just want something that'll work for free trails.

December 17, 2010 at 3:50 amNice article.

Btw, it's homer simpson holding up the credit card :P

December 23, 2010 at 2:24 pmwant a CC????????

January 1, 2011 at 2:20 pmNow look, Raymond made this article for our own info not for actual use by stupid people. You know there could be many FBI agents reading this and could arrest you? It is a federal crime to misuse a credit card and could lead to jail. I myself got arrested because I used an uzi on a police car... Thats a different story though. Stop the idiopathy guys!

February 13, 2011 at 9:33 amthanks for great post. I been working with e-gold long time ago, now starting with liberty reserve and investing in hyips.

October 7, 2012 at 11:23 amI never knew this. I am not sure how or why I will ever need to know about the Luhn's credit card validation test but it is nice to know. This was a well written article with a great explanation. Thank you so much for writing it. I greatly appreciate you sharing it with me.