ISBN Converter and Validator

Every book sold in a shop or catalogued by a library carries an International Standard Book Number. Until 2007 the number had ten digits, and since then it has had thirteen, so a collection of records often mixes both. Systems that need one format must convert the others, and the check digit has to be recalculated, because the two formulas differ. This page validates ISBNs, converts between the formats and shows what each part of the number says.

Two formulas

ISBN-10 multiplies its first nine digits by the weights 10, 9, 8 and so on down to 2, adds the products, and chooses the check character so that the total, including check digit times 1, is divisible by 11. When the needed value is 10, the character X is written. ISBN-13 is simply the same 13 digits as an EAN-13 barcode: the weights alternate 1 and 3 across the first twelve digits, and the check digit brings the total to a multiple of 10.

A worked example

Press Sample to check six numbers. 0-306-40615-2 is a valid ISBN-10; its ISBN-13 form is 9780306406157, and its registration group is the English-language area. Entering 9780306406157 goes the other way and returns 0306406152. 080442957X is valid with check character X and converts to 9780804429573. 978-3-16-148410-0 is a valid ISBN-13 in the German-language group, and its ISBN-10 form is 316148410X. 0306406153 differs from the first in the last character and is rejected; the page gives the correct check character, 2. 9791090636071 is valid, begins with 979, and the page states that 979 numbers have no ISBN-10 form.

Converting by hand

To go from ISBN-10 to ISBN-13, take the first nine digits, write 978 in front, and compute the new check digit with the 1-and-3 weights. For 030640615, that gives 978030640615 and the check digit 7. To go back, drop 978 and the old check digit, and recompute with the ISBN-10 formula. You cannot reuse the old check digit in either direction because the formulas differ.

The registration group

The digits after the 978 or 979 prefix name the registration group, which is a language area or country: 0 and 1 for English-language countries, 2 for French, 3 for German, 4 for Japan, 5 for Russian-language, 7 for China and so on. The page names the group for common ones. The publisher and title elements that follow have lengths that depend on assigned ranges, so the page does not try to split them: that needs the agency’s current range table.

Practical tips

When importing book data from spreadsheets, store ISBNs as text so that leading zeros and the final X survive. Remove hyphens and spaces before comparing, and compare in one format only, converting the other to ISBN-13. Be wary of numbers copied from scanned or OCR text, where 0 and O or 1 and l are confused.

Limits

The check proves a number is well formed, not that a title exists. The page does not look up books or publishers. Everything runs in the browser.

Related tools

• GTIN, EAN and UPC Check Digit Calculator validates the barcode form of an ISBN-13.
• Barcode Generator prints an ISBN as an EAN-13 barcode.
• Luhn Validator uses a different check for card numbers.
• Verhoeff Algorithm Validator shows a stronger check-digit scheme.