ISBN Converter and Validator
Validate ISBN-10 and ISBN-13 numbers and convert between them, one per line. Nothing is uploaded — the checks run on your device.
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ISBN Converter
An ISBN identifies a book. Older books carry a 10-digit ISBN-10; since 2007 new books carry a 13-digit ISBN-13. Both end in a check digit, and an ISBN that begins with 978 can be rewritten in the other length. This tool validates and converts, locally.
How the check digit works
- ISBN-10: multiply the digits by weights 10, 9, ... 1; the total must be divisible by 11. The check character may be
X, standing for 10. - ISBN-13: multiply by alternating weights 1 and 3; the total must be divisible by 10.
- Conversion: ISBN-10 to ISBN-13 adds the 978 prefix and recomputes the check digit; ISBN-13 to ISBN-10 is possible only from the 978 range.
Related tools
This checks a book identifier; for a binary checksum see the the CRC-32 calculator, and for identifier formatting try the the UUID generator.
Frequently asked questions
What does this tool do?
It validates ISBN-10 and ISBN-13 numbers and converts between them, one ISBN per line.
How is the check digit verified?
An ISBN-10 uses a weighted sum with weights 10 down to 1, taken modulo 11. An ISBN-13 uses alternating weights of 1 and 3, taken modulo 10.
How does the conversion work?
An ISBN-10 becomes an ISBN-13 by adding the 978 prefix and recalculating the check digit. An ISBN-13 becomes an ISBN-10 only when it begins with 978.
Why can't a 979 number convert to ISBN-10?
The 979 range was introduced for ISBN-13 because the 978 range was running out; it has no ISBN-10 equivalent.
Are spaces and hyphens okay?
Yes. Spaces and hyphens are ignored, so 978-3-16-148410-0 and 9783161484100 are treated the same.
Does it look up the book?
No. It only checks and converts the number format; it does not query any book database.
Related: the the CRC-32 calculator, the UUID generator, word counter, or browse every browser-only tool on the all tools page.