Example
Valid ISBN-13
ISBN Validator
Validate ISBN-10 and ISBN-13 numbers with their check digits instantly in your browser. Free online ISBN validator that also fills in a missing digit.
Enter the values below, then press Calculate (or press Enter). The calculator updates your results instantly. Try different values to see how your inputs change the outcome.
- ISBN — enter a text value. A typical ISBN would be e.g. 978-3-16-148410-0.
- Review your results — the key output is highlighted, with supporting figures below.
Loading calculator…
Results
Result
| Detail | Value |
|---|---|
| Type | |
| Normalised number | |
| Length |
What is this calculator for?
Verify a book’s ISBN by checking its final check digit.
How to Use This Calculator
Enter the values below, then press Calculate (or press Enter). The calculator updates your results instantly. Try different values to see how your inputs change the outcome.
- ISBN — enter a text value. A typical ISBN would be e.g. 978-3-16-148410-0.
- Review your results — the key output is highlighted, with supporting figures below.
What You'll Need
- ISBN
- a text value · required
About This Calculator
An ISBN’s final digit is a check digit computed from the preceding digits. A single mistyped digit will (almost always) break the checksum.
This validator works for both ISBN-10 (10 digits, check can be 0–9 or X) and ISBN-13 (13 digits), recomputing the expected check digit and comparing it to the one given.
All validation runs locally in your browser.
Worked Examples
Frequently Asked Questions
What does the check digit protect against?
It catches any single-digit error and most two-digit transpositions, so a valid checksum strongly suggests the number was typed correctly.
Can ISBN-10 use a letter?
Only the last digit can be "X" (representing the value 10) in ISBN-10. ISBN-13 uses digits only (a leading 978 or 979 and a numeric check digit).