Ever since I wrote the articles on “Meaning of Numbers on a Debit or Credit Card” and “How To Find If A Credit Card Is Fake”, one thing continuously nagged me- Why are the card numbers so long? Apart from making it difficult for us to remember Won’t it increase the chances of someone accidently typing your card number instead of theirs while making an online transaction?

Well, there is a logical reason for this.

This is done for added security. So that probability of fraudsters coming up with correct card numbers is very less. Let’s understand this in detail.

How many possible values can be there for a 2-digit number? The answer is 100- from 00, 01 and so on till 99. Or to make it more simple, its 10^2, i.e. 100. Similarly for a 3-digit number, possible combinations of values is 1000- 000 to 999, or 10^3.

Card number is generally 16 digits long. So the number of possible 16 digit numbers is 10^16. If every individual of the world owns a card, even then total number of cards will be 10 billion (assuming world’s population to be 10 billion- it is presently close to 7 billion). The probability that a fraudster manages to correctly guess a card number is (10 billion)/ (10^16) = 0.0001% – 1 out of 1 million !!

Of course this does not mean that you should become careless with your card. For there are many other ways one can be conned into revealing sensitive information about credit cards and bank details. So never let your guard down. Oh and please don’t believe someone who tells you that entering your card PIN in reverse in an ATM will bring help- because it is just a popular hoax.

Some day they run out of combinations and will have to make it a 20 digit number or higher, for the same reason we are running out of IP addresses and they are trying to move to IPV6.

I don't think it will happen in near future. And anyway there are cards with 20 digits too. Check out a Maestro card. In fact Visa cards were earlier 13 digits long, they later switched to 16 digit format.

Ohh btw, please consider using your name while commenting, otherwise your comment gets marked as spam and may get deleted. You have the option to add your website in the comment form which gives you a do-follow-link to your blog.

Yes Marin, this is just the first line of defense. There are many more checks in place and obviously the best way to keep it secure is to be careful how you use it. Do not leave your card unattended when in restaurants.

The number of possible ten-digit numbers is 1010 = 10 billion, enough to give a unique 10-digit identification number to every person who is now alive or will be born in the next 50 years

hoho..i think long number credit card for protection from hijack..thx for share

Again amazing post with maths, i love maths, good post and also thanks for popular hoax.

still it is not secure as it should be

Actually i thought that they represent the bank code and country in the number…..

Not exactly but you are somewhat right. To know what these numbers mean, check out "Meaning Of umbers On Debit/Credit Card"

Some day they run out of combinations and will have to make it a 20 digit number or higher, for the same reason we are running out of IP addresses and they are trying to move to IPV6.

I don't think it will happen in near future. And anyway there are cards with 20 digits too. Check out a Maestro card. In fact Visa cards were earlier 13 digits long, they later switched to 16 digit format.

Ohh btw, please consider using your name while commenting, otherwise your comment gets marked as spam and may get deleted. You have the option to add your website in the comment form which gives you a do-follow-link to your blog.

Yes Marin, this is just the first line of defense. There are many more checks in place and obviously the best way to keep it secure is to be careful how you use it. Do not leave your card unattended when in restaurants.

Glad you liked it 🙂

My pleasure 🙂

damm and i thought there is something to do with bank codes/ area codes… thanks for the article!

Its a nice post on credit card. Actually i haven't thought of this question any time.Thanks that you have shared shared this with us.

nice post anshul,that calculation were nice,but card are still secured to only some extent not fully.

good job Anshul its such a nice post using long codes makes other to not to apply any others code.

The number of possible ten-digit numbers is 1010 = 10 billion, enough to give a unique 10-digit identification number to every person who is now alive or will be born in the next 50 years

good work Anshul it is very useful for every body having card

This is really helpful information. hope such types of information will get in future also.

simply useful ty! again.