ISBN converter

Put 978 in front of the first nine digits, drop the old check digit, and work out a new one with weights 1 and 3. The converter does all three steps and shows the math. The result is the same ISBN, not a new one.

The last digit is a check digit worked out from the others, and the two formats use different formulas. ISBN-10 uses modulus 11 with weights 10 down to 2. ISBN-13 uses modulus 10 with weights 1 and 3. So the check digit usually changes even though the rest of the number is the same.

ISBN-10s only ever existed for the 978 range. A 979 ISBN has no 10-digit equivalent, and the International ISBN Agency warns that forcing one creates duplicates and wrong orders. Quote 979 ISBNs in full.

It stands for 10. The ISBN-10 check digit can be 0 to 10, and 10 is written as X so it still fits in one character. ISBN-13s never use X.

The ISBN is still valid, but ISBNs have been 13 digits since 1 January 2007, and the agency asks that the 10-digit form no longer be quoted. Use the ISBN-13 on your cover, copyright page, barcode and metadata.

Hyphens split the ISBN into prefix, country or language group, publisher, title and check digit. Their positions depend on who issued the ISBN, so copy them from your ISBN agency record. If you type an ISBN with hyphens, the converter carries them over.

Check the length (10 or 13), the prefix (978 or 979 for ISBN-13) and the check digit. The converter does all three and tells you the digit it expected, which catches most typos. It cannot tell whether an ISBN has actually been assigned to a book.

No. The converter runs in your browser, including list mode and the CSV download. Nothing you type leaves your device.