ISBN Converter

How to use the ISBN converter

1. Paste an ISBN, with or without hyphens or spaces. The tool tells you whether it's an ISBN-10 or an ISBN-13 and whether its check digit is right.
2. Read the other version. An ISBN-10 becomes an ISBN-13; an ISBN-13 starting with 978 becomes an ISBN-10.
3. Checking a list? Switch to batch mode and paste up to 100 ISBNs, one per line. Copy the results or download them as a CSV file.

The tool checks the format only. It can't tell you whether an ISBN has been assigned to a book, and it never makes one up. Numbers are shown without hyphens, because where the hyphens go depends on registration data the tool doesn't use.

ISBN-10 vs ISBN-13

ISBNs had 10 digits until 2007, when they moved to 13 so the system wouldn't run out of numbers. Every ISBN issued now has 13 digits, but older books still carry ISBN-10s.

• ISBN-10: nine digits plus a check character, which can be X (meaning 10).
• ISBN-13: starts with 978 or 979, then nine digits, then a check digit. It's the number in the barcode on the back of a book.
• Converting: an ISBN-10 becomes an ISBN-13 by adding 978 in front and working out a new check digit. Only 978 ISBN-13s have an ISBN-10 version; 979 numbers were never issued as ISBN-10s.

To turn an ISBN into a barcode for a back cover, use the ISBN barcode generator.

How the check digit works

The last digit of every ISBN is a check digit, worked out from the others, so a typing mistake usually shows up as an invalid number.

• ISBN-13: multiply the first 12 digits by 1, 3, 1, 3 and so on, add them up, and the check digit is whatever brings the total to the next multiple of 10.
• ISBN-10: multiply the first nine digits by 10, 9, 8 and so on down to 2, add them up, and the check digit is whatever makes the total divisible by 11. If that's 10, it's written as X.

If the check digit is wrong, the tool shows the digit that would make it valid. That's only a hint for spotting typos: use it only if it matches the ISBN you were given. For when you need an ISBN at all, see do you need an ISBN for an ebook?