# ISBN-13 Validity

ISBN-13 is the official and modern version of book indexing internationally. This method has been phasing out ISBN-10 since 2007. Just like ISBN-10, the numbers are linked mathematically to a weight to validate the authenticity of a book.

It is very simple to validate an ISBN-13 number, as it is validated using a weighted number system of 1 and 3 repeating.

1,3,1,3,1,3…

To give an example, I will show an ISBN-13 number and explain the process.

978-1932698183

To start we need to remove the dashes and multiply each number by the weight. Here is a graph so you can visualize it easier.

9781932698183

 9 *1 9 7 *3 21 8 *1 8 1 *3 3 9 *1 9 3 *3 9 2 *1 2 6 *3 18 9 *1 9 8 *3 24 1 *1 1 8 *3 24 3 *1 3

Once you have all of the weights applied, add all of the numbers together.

9+21+8+3+9+9+2+18+9+24+1+24+3=

140

Once you have added all of the weighted numbers up, divide that number by 10. If the number is divisible by 10, then the ISBN-13 is valid!

140/10=

14

(This isn’t the only way to check for validity with an ISBN-10 number, but it is a quick way to identify the validity of the book!)

AAAAB AAAAA AAABA ABBAB ABBAA ABAAA BAAAB AABBA ABBAB ABBAB AAABB

Now, you translate the Groups with the grid provided!

Now that you know how to identify the validity of a book, you can now buy a book knowing how to identify it and how to make sure it is valid!