Calculators
ISSN Checksum Calculator
Validate an ISSN checksum or generate its missing check digit privately in your browser.
Enter eight characters to validate an ISSN, or seven digits to generate its check digit. Spaces and hyphens are ignored; the final digit can be X. A valid checksum does not establish that a serial publication is registered.
How ISSN check digits work
Enter a complete eight-character ISSN to validate its checksum, or seven payload digits to generate the final character. Spaces and hyphens are ignored, lowercase x is accepted as the final character, and leading zeros are preserved. Multiply the seven payload digits by weights 8 through 2. The check digit makes the weighted sum plus the check value divisible by 11; X represents 10. For payload 0317847 the weighted sum is 120 and the check digit is 1, giving 0317-8471. For payload 2434561 the check digit is X, giving 2434-561X. A failed validation shows the expected digit without changing the supplied input. ISSNs identify serial publications rather than individual books. This checks checksum arithmetic only: it does not verify assignment, registration, publication existence, or hyphen placement. Input is limited to 100 characters including separators. All processing stays in your browser.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
How do I generate an ISSN check digit?
Enter the first seven digits and select Calculate. The payload 0317847 gives check digit 1 and ISSN 0317-8471.
Why can an ISSN end in X?
The modulus-11 calculation can require a check value of ten. ISSN represents that value with X in the final position.
Does a valid checksum prove an ISSN is registered?
No. The tool checks arithmetic only and does not query serial publication or assignment records.
Can I paste an ISSN with a hyphen?
Yes. Spaces and hyphens are removed before calculation. Leading zeros are preserved and lowercase x is accepted.
Is ISSN the same as ISBN?
No. ISSN identifies serial publications, while ISBN identifies book editions. Use the related ISBN calculator for ISBN checksums.