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Both ISBN formats — the older 10-digit and the current 13-digit standard — include a built-in check digit specifically designed to catch a mistyped or transposed digit.
This validator checks whether an ISBN-10 or ISBN-13 number's checksum is mathematically valid, automatically detecting which format you entered.
How it works
Enter an ISBN (dashes and spaces are ignored). For a 10-digit ISBN, each of the first 9 digits is multiplied by a descending weight (10 down to 2) and summed with the check digit; the total must be divisible by 11. For a 13-digit ISBN, each digit is multiplied by an alternating weight of 1 and 3; the total must be divisible by 10.
- Enter iSBN.
- Click Calculate to see your results.
Examples
A valid ISBN-13
978-3-16-148410-0 is a commonly-cited example ISBN-13 that passes the checksum validation.
Who should use it
- Checking an ISBN for typos before cataloging or ordering a book.
- Validating ISBN input in a library, bookstore, or publishing application.
Industry applications
- Publishing and bookselling
- Library science and cataloging systems
Advantages
- Supports both ISBN-10 and ISBN-13 formats, auto-detected by length.
- Implements the exact official checksum formula for each format.
Limitations
- Cannot verify that an ISBN is actually assigned to a real, published book — checksum validity only.
Common mistakes to avoid
- Assuming a passing checksum confirms the ISBN belongs to a real, published book, rather than just being a validly-formatted number.
- Mistyping the "X" check digit in an ISBN-10 as a zero or omitting it entirely.
Best practices
- Double-check a suspicious or rejected ISBN against the original source material for a possible transcription error.
Tips
- If an ISBN-10 fails validation, double check whether the last character should be an "X" (representing 10) rather than a digit.