Frequently Asked Questions about the ISBN

What is an ISBN?

The International Standard Book Number (ISBN) is a 10-digit number that uniquely identifies books and book-like products published internationally.

What is the purpose of an ISBN?

The purpose of the ISBN is to establish and identify one title or edition of a title from one specific publisher and is unique to that edition, allowing for more efficient marketing of products by booksellers, libraries, universities, wholesalers and distributors.

What is the format of the ISBN?

Every ISBN consists of ten digits and whenever it is printed it is preceded by the letters ISBN. The ten-digit number is divided into four parts of variable length, each part separated by a hyphen.

Where can I find the ISBN?

ISBN numbers are found on back cover of most books near the UPC symbol or barcode. This 10 or 13 digit number uniquely identifies the book. Note: If you cannot find the book's ISBN number by the UPC or barcode, be sure to check inside the book where the copyright information is contained. Books published before 1970 will not have an ISBN number.

Why do some ISBNs end in an "X"?

In the case of the check digit, the last digit of the ISBN, the upper case X can appear. The method of determining the check digit for the ISBN is the modulus 11 with the weighting factors 10 to 1. The Roman numeral X is used in lieu of 10 where ten would occur as a check digit.

What is the format of the new ISBN-13?

Every ISBN will consist of thirteen digits in 2007. The thirteen digit number is divided into five parts of variable length, each part separated by a hyphen.