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ISBN Validator: Check and Convert ISBN-10 and ISBN-13

This free tool checks whether a book number is a valid ISBN-10 or ISBN-13. It shows the correct check digit, converts between the two formats and works with or without hyphens.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

A single wrong digit makes an ISBN useless. Booksellers, librarians and self-publishers check numbers before they order or list a book.

Type or paste an ISBN. Hyphens and spaces are removed for you.

How to Use This Tool

  1. Enter or paste your input in the box or boxes above.
  2. Choose the options, if there are any.
  3. Press the button to run the tool.
  4. Read the result and use the copy button where one is shown.

How the Calculation Works

For ISBN-10 the digits are multiplied by 10 down to 1 and the total must divide by 11. For ISBN-13 the first twelve digits are multiplied by 1 and 3 in turn, and the check digit brings the total to a multiple of 10. For conversion the tool prefixes 978, drops the old check digit and calculates the new one.

Worked Example

0-306-40615-2 is a valid ISBN-10 and converts to 978-0-306-40615-7, which is a valid ISBN-13.

Common Uses

  • Checking book data.
  • Listing on stores.
  • Library work.
  • Data cleaning.

Tips and Common Mistakes

  • An X at the end of an ISBN-10 stands for ten.
  • Only ISBN-13 numbers starting with 978 convert back to ISBN-10.
  • Hyphen positions are not checked.
  • Check the first result against a case you already know, so you can trust the tool for the rest.
  • Nothing you type leaves your device. The work is done by your browser, so it also works with a slow connection once the page has loaded.

Next, you may need the Luhn check digit generator, modulo calculator, prime number checker, GCD and LCM calculator.

Everything runs in your browser. Nothing you type is uploaded, stored or sent to any outside service.

Frequently Asked Questions

The International Standard Book Number. Since 2007 it has 13 digits, and older books have 10.
For ISBN-13, digits are weighted 1 and 3 in turn. For ISBN-10, they are weighted from 10 down to 2 and the check can be X for ten.
No. It only proves the digits are consistent. The tool does not look anything up.
Yes. It adds the 978 prefix and works out a new check digit.

Disclaimer: results are calculated in your browser from the numbers you enter. Check important results before you rely on them for money, health, safety or legal decisions.