ISBN Checker & Converter
Check a book identifier before using it in research notes or source metadata, then convert between compatible ISBN formats when possible.
A check digit protects structure, not bibliographic accuracy
An ISBN-10 uses a weighted modulo-11 check, while ISBN-13 uses alternating 1 and 3 weights and a modulo-10 check. Only a compatible 978-prefixed ISBN-13 can be converted back to ISBN-10 by the supported method; do not assume a 979-prefixed book has an ISBN-10 equivalent.
After generating the formatted identifier, verify the edition, author, publisher and year against the book or official catalog. Two editions of the same title can carry different ISBNs, and a mathematically valid string does not prove that any book was assigned it.
Privacy: bibliography and DOI utility inputs are processed locally in your browser and are not sent to a citation-processing backend.
Formula
ISBN-10 uses a modulo-11 check digit; ISBN-13 uses alternating 1 and 3 weights with a modulo-10 check digit
A valid check digit does not identify the edition you intended
- ISBN-10 0-306-40615-2 passes its check and converts to ISBN-13 9780306406157.
- A valid 979-prefixed ISBN-13 has no corresponding ISBN-10 because the reverse conversion cannot preserve that prefix distinction.
What the result tells you
Use conversion to normalize compatible identifiers and verify the bibliographic record separately.
Before you use the result
The checksum cannot confirm title, binding, publisher or edition. Formats of the same work may use different ISBNs; compare the actual item with an authoritative catalogue.
References for this method
Useful for
- Checking book ISBNs
- Converting ISBN-10 to ISBN-13
- Converting compatible 978 ISBN-13 to ISBN-10
Questions
Can every ISBN-13 be converted to ISBN-10?
No. Only valid ISBN-13 identifiers with a 978 prefix have a corresponding ISBN-10; 979-prefixed ISBNs do not.
Does ISBN validation identify the book?
No. This tool validates and converts the number locally; it does not perform a catalog lookup.