ISBN converter and validator
Type or paste an ISBN with or without hyphens. The tool checks its check digit, tells you whether it is an ISBN-10 or an ISBN-13, and gives the same book number in the other format.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Enter an ISBN-10 or ISBN-13. Hyphens, spaces and an “ISBN” prefix are ignored.
- Read whether it is valid; if not, the tool shows the check digit it should have.
- Copy the ISBN-13 or the ISBN-10.
How it works
- ISBN-10: multiply the first nine digits by 10, 9, 8 … 2 and add them. The check digit is (11 − sum mod 11) mod 11, with 10 written as X.
- ISBN-13: multiply the first twelve digits alternately by 1 and 3 and add them. The check digit is (10 − sum mod 10) mod 10.
- ISBN-10 → ISBN-13: 978 + the first nine digits + a new ISBN-13 check digit.
- ISBN-13 → ISBN-10: only for 978; take digits 4 to 12 and add a new ISBN-10 check digit.
Worked example
0-306-40615-2: 0×10 + 3×9 + 0×8 + 6×7 + 4×6 + 0×5 + 6×4 + 1×3 + 5×2 = 130, and 130 mod 11 = 9, so the check digit is 11 − 9 = 2. Valid.
As ISBN-13: 978030640615 has the weighted sum 93, so the check digit is 10 − 3 = 7: 9780306406157.
Tips
- The barcode on a book (EAN-13) carries the ISBN-13.
- A failed check almost always means a typing mistake; compare with the copyright page.
- Different editions and formats (hardback, paperback, e-book) have different ISBNs.
Frequently asked questions
How do I convert ISBN-10 to ISBN-13?
Put 978 in front of the first nine digits and calculate a new check digit for the 13-digit number. The old check digit is dropped. 0-306-40615-2 becomes 978-0-306-40615-7.
Why does my ISBN-13 have no ISBN-10?
Only ISBN-13s that start with 978 match an ISBN-10. Numbers starting with 979 were issued after ISBN-10 ended and have no 10-digit form.
How is the ISBN-13 check digit calculated?
Multiply the first 12 digits alternately by 1 and 3, add them up, and take (10 − sum mod 10) mod 10. For 978030640615 the sum is 93, so the check digit is 7.
What does the X in an ISBN-10 mean?
It stands for 10. The ISBN-10 check digit can be 0 to 10, and 10 is written as X.
Does it add the hyphens?
No. The position of the hyphens depends on registration group and publisher ranges, so the result is shown without them. Shops and libraries accept ISBNs without hyphens.