ISBN Validator
Validate International Standard Book Numbers (ISBN). Check both ISBN-10 and ISBN-13 formats with checksum verification.
Enter ISBN
Enter with or without hyphens. ISBN-10 can end with X.
Example ISBNs
- ISBN-10: 0-306-40615-2
- ISBN-10 with X: 0-43-965068-X
- ISBN-13: 978-0-306-40615-7
- ISBN-13 (979): 979-10-90636-07-1
How ISBN Validation Works
ISBN (International Standard Book Number) is a unique identifier for books. There are two formats: ISBN-10 (older) and ISBN-13 (current standard).
ISBN-10 Format (Legacy):
- 10 digits total
- Last digit is a checksum (0-9 or X, where X = 10)
- Checksum calculated using modulo 11 algorithm
- Example: 0-306-40615-2
ISBN-13 Format (Current):
- 13 digits total
- Starts with 978 or 979 (GS1 prefix for books)
- Last digit is a checksum (0-9)
- Checksum calculated using modulo 10 algorithm
- Example: 978-0-306-40615-7
When ISBN is Used:
- Book publishing and distribution
- Library cataloging systems
- Online bookstore inventory
- Book sales tracking and royalties
- ISBN is required for most retail book sales
ISBN-10 vs ISBN-13 at a glance
Books carry one of two ISBN formats. This validator detects which one you entered by its length and applies the matching checksum:
| Feature | ISBN-10 (legacy) | ISBN-13 (current) |
|---|---|---|
| Digits | 10 | 13 |
| Prefix | none | 978 or 979 |
| Check digit | modulo 11 (0–9 or X) | modulo 10 (0–9) |
| Adopted | before 2007 | 2007 onward |
| Example | 0-306-40615-2 | 978-0-306-40615-7 |
Frequently Asked Questions
What is the difference between ISBN-10 and ISBN-13?
ISBN-10 is the older 10-digit format; ISBN-13 is the 13-digit standard that publishing adopted in 2007. ISBN-13 prefixes the number with 978 or 979 and uses a different check-digit formula (modulo 10 instead of modulo 11). All new books carry an ISBN-13, but older ISBN-10s remain valid.
Can I convert an ISBN-10 to ISBN-13?
Yes. Take the first 9 digits of the ISBN-10 (drop its check digit), put 978 in front, then recalculate the check digit with the ISBN-13 modulo 10 formula. For example, 0-306-40615-2 becomes 978-0-306-40615-7. The 979 prefix is used for newer allocations that have no ISBN-10 equivalent.
What is the X at the end of some ISBN-10s?
It is the check digit standing in for the value 10. ISBN-10 uses a modulo 11 checksum, so a valid check digit can be anything from 0 to 10 — and since 10 will not fit in a single slot, the Roman numeral X is used instead. ISBN-13 avoids this because its modulo 10 check digit is always 0 to 9.
Does a valid ISBN mean the book exists?
No. This validator only confirms the format and checksum are mathematically correct. It cannot tell you whether the ISBN was ever assigned to a real, published title — for that you would query an ISBN registry or a bookseller’s catalog. A valid checksum just means the number is not a typo.
How is the ISBN-13 check digit calculated?
Multiply the first 12 digits alternately by 1 and 3, add the results, and the check digit is whatever makes that total a multiple of 10. It is the same scheme as the EAN-13 barcode, which is why an ISBN-13 scans like any retail product. The validator runs exactly this calculation.