What Is an ISBN Number?

Updated on February 15, 2018
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Heidi Thorne is a self-publishing expert, nonfiction book editor, author of 21+ books and eBooks, and a former trade newspaper editor.


One of the decisions you need to make when self-publishing is about your ISBN number. What you decide can have implications for the future of your book or eBooks.

What Is an ISBN Number for Books?

ISBN is an acronym that stands for International Standard Book Number. It is a unique number assigned to a book and its format helps booksellers and libraries find books and who published them. These numbers also help track retail book sales for the publishing industry. However, they are only used for books and are not used for publications such as magazines.

The ISBN number is printed on the lower right back cover above the barcode and on the page containing your book’s copyright information.

Other than for purposes of finding books and sales tracking, these numbers do not provide any copyright protection or any other benefits. They’re nothing magical. They just help books get found and tracked.

How Did ISBN Numbers Get Started?

ISBN numbers were developed in the late 1960s when Britain’s largest book retailer, W.H. Smith, decided to computerize their warehouse. They devised the Standard Book Number system. The International Organization for Standardization (ISO), with input from several countries including the United States, moved to adopt the British Standard Book Number as an international standard. In 1970, the ISBN standard was established by the ISO. It is governed internationally by the International ISBN Agency. (Source: ISBN.org)

Where Do ISBN Numbers Come From?

Publishers and self-published authors can purchase ISBN numbers for their books through an ISBN registrar company in their home country. In the United States, the registrar is R. R. Bowker (bowker.com). The purchase usually includes the privilege of obtaining listings for their books in a book database, such as Bowker's Books in Print®, used by booksellers and libraries.

What’s the Difference Between a 10-Digit and 13-Digit ISBN Number?

ISBN numbers are either 10 or 13 digits. Both 10 and 13 digit ISBN numbers include coding for the country of publication, publisher, title, and a check digit.

In January 2007, the 13-digit standard was established. A 10-digit number can be converted into its 13-digit equivalent with an ISBN conversion tool. In the United States, the conversion tool is available on ISBN.org.

When I've published on Amazon Createspace or KDP, I've received both the 10-digit and 13-digit ISBN number versions for my books.

Isn’t an ISBN a Barcode?

No. However, to facilitate retail sales (e.g. for scanning at checkout at a bookstore) and industry sales reporting, a barcode can be generated for an ISBN, which would then be included on the lower back right cover of a book.

ISBN registrar companies, such as Bowker, usually charge a fee to generate a barcode for a particular ISBN number. This fee is in addition to the fee to obtain the number. The barcode graphic will also include the price of the book.

Does Everything I Self-Publish Need an ISBN Number?

If you are just producing and selling your book on your own directly to readers, an ISBN number is not required.

Each book that you plan to offer through normal book distribution channels (bookstores, online booksellers, wholesalers, distributors, libraries, universities, etc.) will require an ISBN number.

Also, if a title is offered in multiple formats, a unique ISBN number is required for each. So if a title has a print, eBook, and audio edition, three ISBN numbers would be purchased and assigned, one for each format.

Similarly, each succeeding edition of a book—e.g., 2nd edition, revised edition, etc.—should have its own ISBN number, and each format of the succeeding edition (print, audio, eBook, etc.) still needs a separate ISBN number. Because you have the capability to upload revised manuscripts on either Createspace or Kindle Direct Publishing (KDP), it’s easy to forget this. (Guilty for one of my books!) If the changes, updates, or corrections are minor—such as for updated contact information or a few typos—I’ve just uploaded the changed manuscript so that the best version of it is available. But when the changes to the actual content are substantial in terms of additions or revisions, a new ISBN should be assigned for the substantially changed edition.

Very active publishers often opt to purchase banks of ISBN numbers to conveniently draw from. This avoids having to secure an ISBN number every time one is needed. But until the publisher officially assigns and connects a specific ISBN number to a book's edition and format through the home country's ISBN agency, the number means nothing and will not show up in databases.

Amazon Createspace Offers a Free ISBN for My Books. Should I Use It?

Amazon Createspace and other self-publishing platforms often offer free ISBN numbers to their participating self-published authors as a benefit. Also, the self-publishing platform takes care of assigning the ISBN number to the book with the appropriate ISBN agency. However, there is a hidden cost to taking advantage of this offer.

The free ISBN will be associated with Amazon Createspace, KDP, or another self-publishing platform as the publishing contact. Should self-publishers ever wish to publish elsewhere (such as on another self-publishing platform) or even print on their own, they would need to decommission the existing ISBN number and set up a new ISBN number for any new printings and publication of the title. This can result in confusion on sites such as Amazon where copies of both the old and new editions may be offered. The old edition could show as unavailable or out of print, and customers may wonder if this new edition is the same as the old one.

So purchasing and using your own ISBN numbers can give you, as a self-publisher, more control over the future of your books. Fortunately, you are given the option of providing your own purchased ISBN during the publishing process on both Createspace and KDP.

I did purchase a couple of ISBN numbers in my early days of self-publishing many, many years ago. However, more recently, I’ve chosen to go with the free ISBN numbers offered by Amazon Createspace and KDP. I didn’t believe that the revenues and royalties I would make from many of my print or eBook titles would justify the cost of the numbers, barcodes, and maintaining them. As well, I didn’t think that the opportunities for sales outside the Amazon universe (such as in bookstores) were relevant or prevalent enough to generate significant non-Amazon sales. But I made this choice after going through an analysis of my options. This may not be a choice for you.

Don’t make your choice based solely on cost. But carefully compare the costs of purchasing and managing your own ISBNs against potential sales opportunities and your future publishing goals since ISBN numbers are an investment.

Amazon KDP Uses an ASIN for Kindle eBooks. Is that the Same as an ISBN?

No. Amazon KDP assigns an ASIN number to Kindle eBooks—and every product on Amazon!—for its own inventory and sales tracking purposes. It is not connected to ISBN in any way.

ASIN numbered eBooks do not have an ISBN number and are not listed in resources such as Bowker’s Books in Print database. This is why some KDP self published authors opt to purchase and provide their own ISBN numbers for their Kindle eBooks in order to improve their chances of being found outside of the Amazon universe.

And if you choose to publish a print edition of your Kindle eBook on KDP, you’ll need an ISBN number assigned to it.

Will Having an ISBN Improve My Chances of Making Sales?

Yes and no. Yes, in that readers who may be looking for your book can go to a bookstore or library that can order it direct from the publisher should it not be immediately available on the shelves (or virtual eBook shelves).

However, just being listed in a database such as Books in Print does not mean that any outreach marketing is done by your ISBN agency, bookstores, or libraries to connect readers and distributors to your book. So an ISBN number merely facilitates sales that you have generated through your own sales efforts.

Disclaimer: Both the publisher and author have used their best efforts in preparation of this information. No representations or warranties for its contents, either expressed or implied, are offered or allowed and both parties disclaim any implied warranties of merchantability or fitness for your particular purpose. The advice and strategies presented herein may not be suitable for you, your situation or business. Consult with a professional advisor where and when appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other damages, including but not limited to special, incidental, consequential or punitive, arising from or relating to your reliance on this information.

© 2018 Heidi Thorne


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  • heidithorne profile image

    Heidi Thorne 3 weeks ago from Chicago Area

    Hi Dianna! I'm surprised that was a topic in a H.S. marketing class. They can definitely be important when doing research. Thanks for stopping by and your kind words. Have a great week!

  • teaches12345 profile image

    Dianna Mendez 3 weeks ago

    Good write on the topic. I had to teach the meaning and importance of ISBNs in my high school marketing classes. Your article would have been a great reference for them.

  • heidithorne profile image

    Heidi Thorne 3 weeks ago from Chicago Area

    Hi Eric! Glad you found it helpful. Thanks for stopping by and have a terrific day!

  • EricFarmer8x profile image

    Eric Farmer 3 weeks ago from Phoenix Arizona

    I heard of ISBNs but I wasn't quite sure what they for. I know now. This is a very helpful Hub.

  • heidithorne profile image

    Heidi Thorne 4 weeks ago from Chicago Area

    Natalie, even this explanation just scratched the surface! But glad it offered some info for you. Appreciate you stopping by and have a great week!

  • heidithorne profile image

    Heidi Thorne 4 weeks ago from Chicago Area

    Suhail, glad to offer the info! Appreciate you stopping by. Have a great week!

  • Natalie Frank profile image

    Natalie Frank 4 weeks ago from Chicago, IL

    I thought I knew about ISBN numbers but you have presented a lot of information that I was not familiar with. Thanks for the info!

  • Suhail and my dog profile image

    Suhail Zubaid aka Clark Kent 4 weeks ago from Mississauga, ON

    Hi Heidi,

    Never gave importance to ISBN numbers. Now I know almost everything about them, thanks to this article.




  • heidithorne profile image

    Heidi Thorne 4 weeks ago from Chicago Area

    Linda, glad to share! There's so much to publishing these days. Thanks so much for stopping by and have a great weekend!

  • AliciaC profile image

    Linda Crampton 4 weeks ago from British Columbia, Canada

    You know so much about publishing, Heidi. I always learn something new when I read your articles! Thank you for increasing my knowledge.

  • heidithorne profile image

    Heidi Thorne 4 weeks ago from Chicago Area

    Flourish, glad to clarify! Also, that is interesting that reselling popular books to and through Amazon and the like isn't taking off. Hmm...

    I think the primary explanation for that is that book popularity is short lived. True, backlist titles can be sold for even decades after publishing. But after the big initial rush, it slows down to a crawl.

    Thanks for stopping by and adding your experience to the conversation! Have a great day!

  • heidithorne profile image

    Heidi Thorne 4 weeks ago from Chicago Area

    Brian, glad to see that the ISBN system has been a help to you in your librarian adventures! And, yes, thank for clarifying the ISSN situation. (I didn't want to completely confuse everyone with delving into that.)

    Thanks for sharing your experience and expertise with us! Have a great day!

  • FlourishAnyway profile image

    FlourishAnyway 4 weeks ago from USA

    I have wondered why the 10 vs. 13 number ISBN and now I know! It’s interesting that when you try to sell popular used books purchased at Target to Amazon or other resellers nobody wants them.

  • B. Leekley profile image

    Brian Leekley 4 weeks ago from Kalamazoo, Michigan, USA

    ISBN numbers have many uses and are a big convenience. I've seen used book dealers in thrift shops and at garage sales using a smart phone app to scan ISBN numbers to learn which books are in demand. Back in the 1980s when I was book dealing, I had to guess, and I had a store full of books that I thought would sell fast and didn't. These days I'm librarian at my church. I use LibraryThing to catalog the books, and cataloging a book published since the 1970s is simply a matter of typing the ISBN number. The bibliographic information appears, thanks to a computer at Library of Congress or at some other major library or at Amazon communicating with LibraryThing's computer and mine.

    Magazines and other serial publications use an ISSN number (International Standard Serial Number).

  • heidithorne profile image

    Heidi Thorne 4 weeks ago from Chicago Area

    Mary, glad you found it useful. It can be very confusing at times. Took me a while to figure it all out, too. Thanks so much for stopping by and have a wonderful day!

  • heidithorne profile image

    Heidi Thorne 4 weeks ago from Chicago Area

    Bill, I figured you'd understand the whole ISBN issue.

    Well, we're up to the low 40s today. So we're sweltering. :) Thanks for stopping by and for the invite to the sunny climes of Olympia!

  • aesta1 profile image

    Mary Norton 4 weeks ago from Ontario, Canada

    This is very helpful. This is an area that I still have to research had you not written it here. It is also very clear. Thank you.

  • billybuc profile image

    Bill Holland 4 weeks ago from Olympia, WA

    Great explanation of something I actually understand. :) The Heidi School of Marketing continues.

    How's that weather? Warmed up any? You can always move to balmy Olympia to thaw out in the winter. :)