ISSN Validator

About this calculator

This tool checks whether an 8-digit ISSN (International Standard Serial Number) is valid by recalculating its check digit using a mod-11 weighted checksum: each of the first seven digits is multiplied by a descending weight from 8 to 2, the products are summed, and 11 minus the remainder (mod 11) gives the check digit — where a remainder of 1 corresponds to the letter 'X'.

Librarians, publishers, and researchers cataloging journals, magazines, and other periodicals use it to catch a mistyped or misprinted ISSN before citing a source or entering it into a library system. Enter the 8-character ISSN (with or without the hyphen) to check its check digit.