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Understanding ISBNs and What They Mean for Your Book

Q: What is an ISBN, and what’s its purpose? Can I apply for one without being a company/publisher? —Kathryn N.

A: An International Standard Book Number (ISBN) is a 13-digit number that identifies a book for purposes of commerce and supply chains (before 2007 it was a 10-digit number, in case you see it that way in older books). It’s a mandatory sales tool, as it’s the number that bookstores, wholesalers and distributors use to keep track of books.

The number is composed of five parts: the 978 code, group/country identifier, publisher identifier, the title identifier and check digit. The 978 code is used to help calculate the check digit (explained below). The following two sets of numbers identify a national or geographic grouping of publishers, so you know the country where the book was published and the publisher of the book within that area.

Next is the title identifier, which is the number assigned to the specific title. At the end of the long number is the check digit, which is used to detect transcription errors and to validate the ISBN. Sometimes this last “digit” is an “x.” In layman's terms, a check digit is defined as "something writers don't have to worry about."

The numbers are assigned by ISBN group agencies to publishers, e-book publishers, audio cassette and video producers, software producers, and museums and associations with publishing programs. And, while you technically need to be one of these to get an ISBN, if you’re self-publishing a book, you qualify as a publisher.

To get an ISBN in the United States, go to There you can request the necessary forms. The cost for one is roughly $125, though you can typically buy them in bulk and at a cheaper rate.

If you’re publishing in Canada, contact the National Library of Canada ( for more information.

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