ISBN Validator
Check whether an ISBN 10 or ISBN 13 is well formed, and convert between the two formats.
How this tool works
An ISBN identifies a book edition and is either 10 or 13 characters long. The 13 character form is the current standard and is what nearly every new book carries; the 10 character form is the older one and is still seen on older editions and in older catalogues.
Both forms carry a check digit computed with a different modulus. The ISBN 10 uses a weighted sum of 10 to 1 with the last character able to be X, and the ISBN 13 is the EAN 13 with a check digit computed modulo 10. The ISBN 13 also differs in that the 978 prefix replaces the 978 or 979 group element that the ISBN 10 encoded, and the two can be converted from one another.
Worked example
| Step | Value |
|---|---|
| ISBN 13 | 9780306406157 |
| EAN check | 7 |
| Group element | 978, English language |
| Registrant | 030640615 |
| Check | Valid, the weighted sum is a multiple of 10 |
The last character of an ISBN 10 can be X, which represents a check value of ten. The ISBN 13 uses digits only.
When to use it
- Validate an ISBN typed into a book order form
- Clean a catalogue import and report the failures
- Convert an ISBN 10 to an ISBN 13 for a modern system
- Confirm that the group element matches the intended language
Frequently asked questions
What is an ISBN?
International Standard Book Number: an identifier for a specific book edition, either 10 or 13 characters long, carrying its own check digit.
What is the difference between ISBN 10 and ISBN 13?
ISBN 13 is the current standard and is the EAN 13 with a 978 prefix. ISBN 10 is the older form with a weighted sum check and a possible trailing X. A 10 character number can be converted to a 13 character one.
What do the first three digits mean?
The group element: 978 for books generally, 979 for other categories, and the next digit identifies the language or region of the registrant, with 0 and 1 reserved for English-language publishers.
Does a valid ISBN mean the book exists?
No. It means the number is internally consistent. A valid ISBN can be assigned to a book that was never published, which happens with advance registrations.
Why does an ISBN 10 sometimes end in X?
Because its check value can be ten, and X is used for ten since the field is ten characters wide.
Can I convert an ISBN 10 to an ISBN 13?
Yes, by prefixing 978, recomputing the check digit and dropping the old one. The reverse conversion is also possible, since the 978 prefix is recoverable from the registration group.