What Is the Checksum of an ISSN Number?

The Checksum of an ISSN Number is the last digit of the ISSN number.

For example, "2719-6488" is the ISSN for the print version of "Journal of Mother and Child". The last digit 8 is the checksum, which is calculated using the Mod11 algorithm.

Here is the Mod11 algorithm to carry out the checksum calculation:

1. Each of the first seven digits of the ISSN is multiplied by its position number counting from the right. Using "2719-6488" as an example, the first digit "2" is multiplied by its position number "8", resulting "16".

2. Add all 7 products from step 1. Using "2719-6488" as an example, the sum is:

2*8 + 7*7 + 1*6 + 9*5 + 6*4 + 4*3 + 8*2 = 168 

3. Take the remainder from the sum modulo 11. Continue with the above example, the remainder is:

168 % 11 = 3 

4. If the remainder is 0, then the checksum is 0.

5. If the remainder > 0, then the checksum is calculated by subtracting the remainder from 11. Continue with the above example, the checksum is:

11 - 3 = 8 

6. If the checksum is 10, convert it to letter X.

⇒ URN for ISSN Number

⇐ What Is ISSN (International Standard Serial Number)

⇑ Introduction of ISSN

⇑⇑ ISSN (International Standard Serial Number)