The algorithm is:

- Multiply each digit in the credit card by its "weight". If a charge card has an even number(16 digit card number) of digits, the first digit has a weight of 2, otherwise the digit has weight of 1. Afterwards, the weights of the digits alternate 1,2,1,2.
- If any digit has a weighted value that is more than 9, Subtract 9.
- Add together the weights of all the digits, modulo 10.
- the result should be zero for a valid credit card.

Examples:

Here is the card number: 3728 024906 54059

The above charge card has 15 digits. the number is odd, So the first digit has a weight of 1. to compute the check digit, we multiply:

(3*1),(7*2),(2*1),(8*2),(0*1),(2*2),(4*1),(9*2),(0*1),(6*2),(5*1),(4*2),(0*1),(5*2),(9*1)

which is:

3 14 2 16 0 4 4 18 5 0 12 5 8 0 10 9

Substract 9 from every value greater than 9, and add them together:

3+5+2+7+0+4+4+9+0+3+5+8+0+1+9 = 60

This gives a check of 0, because 60 mod 10 = 0; Hence the Credit card is Valid.

Here is another card number : 4129 0370 8071 2254

The above charge card has 16 digits. the number is odd, So the first digit has a weight of 2. to compute the check digit, we multiply :

(4*2),(1*1),(2*2),(9*1),(0*2),(3*1),(7*2),(0*1),(8*2),(0*1),(7*2),(1*1),(2*2),(2*1),(5*2),(4*1)

which is :

8+1+4+9+0+3+5+0+7+0+5+1+4+2+1+4 = 54 mod 10 = 4

Hence the credit card is Invalid.

Academic Honesty!

It is not our intention to break the school's academic policy. Projects posted are only used as a reference
and should not be submitted as is. We are not held liable for any misuse of the solutions.
Please see the frequently asked questions page
for further questions and inquiries.

Kindly fill out the form.
Please provide a valid email address and we'll get back to you in less than 24 hours.
We will be sending an invoice through PayPal upon confirmation.
We are a non profit organization however we need an amount to keep this organization running,
and to be able to complete our research and development.