ISBN Validator & Converter
Validate ISBN-10 and ISBN-13 codes and convert between formats. Check if book identifiers are correctly formatted.
About ISBNs
- ISBN-10
- Used before 2007. 10 characters with last digit as check (0-9 or X).
- ISBN-13
- Current standard since 2007. 13 digits starting with 978 or 979.
- Conversion
- ISBN-10 can always convert to ISBN-13 (978 prefix). ISBN-13 with 979 prefix cannot convert to ISBN-10.
What is an ISBN?
An ISBN (International Standard Book Number) is a unique numeric identifier assigned to books and book-like products. Every edition and format of a book (hardcover, paperback, ebook) receives its own ISBN, enabling accurate identification in supply chains, libraries, and retail systems.
ISBNs are managed by the International ISBN Agency and assigned through national agencies. In Australia, this is Thorpe-Bowker; in the US, it’s Bowker.
ISBN-10 vs ISBN-13
ISBN-10 was the original format, used from 1970 until 2007. It contains 10 digits arranged as:
- Group identifier (country/language)
- Publisher code
- Title identifier
- Check digit
Example: 0-306-40615-2
ISBN-13 became the standard in 2007 to align with EAN-13 barcodes used globally. It adds a 978 or 979 prefix:
- EAN prefix (978 or 979)
- Group identifier
- Publisher code
- Title identifier
- Check digit
Example: 978-0-306-40615-7
How ISBN validation works
Both formats include a check digit that validates the other digits are correct.
ISBN-10 check digit: Calculated using modulo 11. Each digit is multiplied by its position (1-10) from the left, summed, and the result modulo 11 must equal 0. The check digit can be 0-9 or X (representing 10).
ISBN-13 check digit: Calculated using modulo 10. Odd-positioned digits are multiplied by 1, even-positioned by 3, summed, and the check digit makes the total divisible by 10.
A single transposed or mistyped digit will cause validation to fail, catching data entry errors.
Converting between formats
ISBN-10 to ISBN-13:
- Add the 978 prefix
- Drop the original check digit
- Calculate the new ISBN-13 check digit
ISBN-13 to ISBN-10:
- Only works for ISBNs starting with 978
- Remove the 978 prefix
- Drop the ISBN-13 check digit
- Calculate the new ISBN-10 check digit
ISBNs beginning with 979 cannot be converted to ISBN-10 as this prefix didn’t exist in the old system.
Why ISBNs matter
Unique identification - Every book edition has a unique identifier, preventing confusion between formats, editions, and translations.
Supply chain efficiency - Publishers, distributors, retailers, and libraries use ISBNs to track inventory, process orders, and manage catalogs.
Metadata linking - ISBNs connect to bibliographic databases containing title, author, publisher, and subject information.
Sales tracking - Industry sales data relies on ISBN reporting from retailers and wholesalers.
Common ISBN errors
Transposition - Swapping two adjacent digits is the most common entry error. The check digit catches these.
Missing hyphens - Hyphens improve readability but aren’t required. 9780306406157 is identical to 978-0-306-40615-7.
Incorrect format - Mixing up ISBN-10 and ISBN-13, or using the wrong check digit calculation.
Reuse - Each format and edition needs its own ISBN. Reusing ISBNs causes catalog confusion.
Who needs ISBNs?
Publishers - Required for distribution through traditional book trade channels.
Self-published authors - Optional but recommended for wider distribution and professional appearance.
Libraries - Use ISBNs for cataloguing and inter-library loans.
Retailers - Rely on ISBNs for inventory management and ordering.
Ebooks - Each ebook format (EPUB, Kindle, PDF) should have its own ISBN.
How this tool works
Enter an ISBN-10 or ISBN-13 to validate its check digit and convert between formats. The tool identifies which format you’ve entered, validates the check digit, and provides the equivalent in the other format where possible. Powered by a QuantCDN Edge Function.