image of curved library shelves in a dark/shadowy setting; ISBNs: Demystifying the digits

Originally published May 25, 2020; most recently updated July 25, 2023.

When I presented “Self-publishing 101” at a conference, one of the biggest topics during the Q&A was ISBNs. Lots of questions and lots of confusion surfaced. ISBNs are one of the elements of indie publishing that took me a long time to figure out, so if you’re puzzled by them, you’re in good company.

In this article, we’ll cover the basics of ISBNs as well as ISBN-related logistics to pay attention to when publishing via KDP and IngramSpark, the two major self-publishing platforms.

What is an ISBN?

ISBN stands for International Standard Book Number. And it’s just what it sounds like: a unique identifying number for your book. It is a global standard and required by most retailers. Through December 2006, ISBNs were 10 digits; now they are 13 digits.

An ISBN usually looks something like this: 978-1-945209-05-5.

  • The first element (978) indicates it is an ISBN.
  • The second element (1) indicates country or language.
  • The third element (945209) indicates the publisher.
  • The fourth element (05) indicates the title and format.
  • The fifth element (5) is a check digit (a number that verifies the other digits were entered correctly).

When someone looks up a book, the owner of the ISBN is listed as the publisher of record. (Note: The ISBN is separate from copyright; owning an ISBN does not necessarily mean you hold the copyright.)

In addition to being part of your book’s metadata, the ISBN is usually located on the back cover of a book and listed in the front matter along with the publisher, copyright, and so on.

How do I get an ISBN? What does it cost?

The publisher acquires the ISBN—and this includes author-publishers, i.e., those who are self-publishing.

ISBNs are distributed by country. In the US, ISBNs can be purchased from Bowker Identifier Services.

As of November 2021, Bowker charges:

  • $125 for a single ISBN
  • $295 for 10 ISBNs
  • $575 for 100 ISBNs
  • $1500 for 1000 ISBNs

(Note: KDP and IngramSpark offer free or discounted ISBNs. I recommend getting your own. More info below.)

Once you’ve purchased a block of numbers, you can hold them until you are ready to assign them to specific books. When you assign a title to an ISBN, it gets added to Bowker’s Books In Print database, which is used by publishers, retailers, and libraries. (Read more Bowker FAQs.)

If you’re based outside the US, you’ll have to find your national ISBN agency to determine the process for getting ISBNs. For example, in Cyprus, ISBNs are provided by the Cyprus Library and are free; the application process includes assigning the ISBN to a specific book.

How many ISBNs do I need?

You need an ISBN for each version of your book: hardback, paperback, ebook, audiobook, large print, and so on. Got a fancy illustrated special edition? It needs its own ISBN. Doing a color version of a book already in black and white? Again, it needs its own ISBN.

Most of my clients have at minimum a paperback and ebook, so they need a minimum of two ISBNs. Many indie authors quickly realize that it makes sense to get a block of 10 ISBNs even if they are only planning on one book in paperback, hardback, and ebook. Authors who plan to create multiple books might want to consider the block of 100 in order to keep the per-unit cost down.

Do I really need an ISBN for my ebook?

Some online retailers (like Amazon) do not require an ISBN for an ebook. Amazon will assign an ASIN (Amazon Standard Identification Number) instead.

However, many online retailers DO require ISBNs for ebooks, e.g., iBooks and Kobo. Additionally, libraries require ISBNs on ebooks.

If you don’t assign an ISBN up front, you may end up with multiple ISBNs (for example, if you get a free one on one platform, then another on another platform) or multiple other identifiers (the equivalent of Amazon’s ASIN) for the same ebook. All this can do is muddy the waters for people looking for your book.

Even if initially you’re publishing only a Kindle version, I recommend assigning your ebook an ISBN so that in the future it can be clearly identified and sold on as many platforms as you’d like.

Do I need a separate barcode?

sample ISBN barcode

The ISBN barcode is a machine-readable version of the ISBN—the larger barcode at left in this image (the price is at right). You’ll see the human-readable digits above and below the barcode.

If you never plan to sell in a retail setting, you don’t need a barcode; however, I recommend having one simply because it is standard practice.

Bowker will try to sell you a barcode on top of the 13-digit number you purchase, but there is no need to pay for a barcode.

If you use KDP or IngramSpark to self-publish, they will generate a barcode for you based on the digits you provide. If you use KDP’s cover creator, it will create a barcode for you; likewise with IngramSpark’s cover template creator. If you create your own cover without a barcode and upload it to KDP, KDP will add a barcode using the number you provide.

You can also search online for free barcode creators. Just be sure to test that the barcodes actually work (use your phone’s camera or download a scanner app to your phone and test it to make sure it reads the numbers correctly).

Do I need the price in my barcode?

In addition to the ISBN barcode, you can have a supplemental barcode that includes the price—the smaller barcode at right in this image. The price is indicated in human-readable form as a five-digit number, in this case 52495. The first digit indicates the currency, e.g., 5 is the code for US dollars. The next four digits are the price, in this case $24.95.

Most barcode generators will ask if you want to include the price in the barcode. And there are actually three barcode variations you could choose:

  • ISBN barcode only with no supplemental price barcode.
  • ISBN barcode and price barcode with no actual price in it. You’ll notice books like this have a “price” of 90000.
  • ISBN barcode and price barcode with the price (as shown).

Include the price in the barcode:

  • If you plan to sell in retail stores. This is standard practice and an expectation for retailers.
  • As a marketing strategy. For example, if you plan to do bulk sales, you may want to anchor the perceived value at $24.95 even though the volume price may be $17.95.

You could skip the price in the barcode:

  • If your primary sales will be online and/or if you will be handling them in person.
  • If you think you might change the price of your book, e.g., for different events.

When do you buy and assign ISBNs?

In the US, you can purchase your ISBNs any time before publication and hold them indefinitely. You must assign your ISBN to your book prior to publication.

If you plan to request US Library of Congress (LOC) cataloging, be sure to assign the ISBN well in advance of publication to allow for LOC processing time.

One tactical note: You must have your title finalized before assigning the ISBN. If you change the title, you need a new ISBN. I mention this because I sometimes have clients who want to change titles all the way up until just before publication. Be sure to recognize the potential snags that that approach can throw into your timeline (not to mention the crimp it puts in your pre-launch marketing).

Can you buy a block of ten ISBNs and then resell them?

ISBNs cannot be resold. Ownership of ISBNs can be transferred for an entire block (e.g., when one company buys another), but ownership of individual ISBNs cannot be.

If you find someone other than Bowker selling ISBNs, exercise caution: they will likely end up listed as the publisher of record.

What about the free ISBNs from KDP and IngramSpark?

When self-publishing on KDP and/or IngramSpark, you can get an ISBN for free. If cost is an issue, this is a nice benefit; however, it comes with a few strings…

  • The free ISBNs can be used only on the platform where you acquired them and can limit your distribution options.
  • The “Publisher” field (e.g., on your Amazon product page) will show “Independently published” rather than your publisher or imprint name. On IngramSpark the publisher will be listed as “Indy Pub.”
  • My understanding is that your book information will get into Bowker’s Books In Print database, but to the best of my knowledge, you will not have access to update that information directly.

One final string that may or may not matter to you: while many readers won’t care who is listed as the publisher, many bookstores will. My sense in talking to bookstores is that when they do not carry books published through KDP, it is for two primary reasons:

  1. If the book is not available and returnable via Ingram (the book distributor, not IngramSpark the self-publishing arm), it is too inconvenient for them. (KDP’s expanded distribution actually does go through Ingram; however, the books are not returnable.)
  2. They don’t want to support the competitive 800-pound gorilla, Amazon.

Do bookstores have the same reaction to IngramSpark’s free ISBN? To date, I have not heard of this being an issue. (Let me know if you have direct experience to the contrary.)

How do I use my own ISBN on KDP and IS? Any tips I should know?

Now there are a couple of tricky spots to be aware of when using your own ISBN.

Using Your ISBN on KDP

Let’s look at KDP first:

  • When you upload your files to KDP, they do a check against Bowker to make sure your imprint matches what is on file. If there is a mismatch, you won’t be able to proceed.
  • When KDP does the check, they are also looking for whether the ISBN is in use elsewhere, e.g., on IngramSpark. If it is in use elsewhere, you will not be able to use KDP’s Expanded Distribution.
  • In fact, using your own ISBN appears to limit some of the Expanded Distribution options, regardless of whether the ISBN is in use elsewhere. (I am having trouble finding any nitty-gritty details in KDP’s Help, and I don’t use this option enough to have recent first-hand experience.) However, if you plan to use a KDP–IngramSpark combo, this is not a problem.

Using your ISBN on IngramSpark

On IngramSpark, you can assume they do a check against Bowker as well. However, the question of whether the ISBN is already in use is less of an issue. Here’s why…

When IngramSpark makes your book available for distribution, they basically send a data feed to all their distributors, including Amazon. The distributors get to decide (presumably via some algorithm) whether to accept the data and list your book for sale. If IngramSpark sends the data feed to Amazon and Amazon is already listing the KDP version of your book with the same ISBN, they will not accept the IngramSpark listing.

The Combo Strategy

Many indie authors use both KDP and IngramSpark for the same version of their book, typically a paperback. (Remember, it has to be the exact same book to use the same ISBN–same trim size, cover format, etc.) Using KDP is believed to give your book a boost in the Amazon search algorithm, and author copies (books purchased at cost) are usually less expensive than those from IngramSpark; however, IngramSpark gives you better access to bookstores and in some situations can pay higher royalties. So using both platforms–KDP for Amazon and IS for everything else–is believed to provide the best of both worlds.

If you plan to use both platforms, here’s my suggestion:

  • Buy your own ISBNs.
  • Set up KDP so that the KDP data populates the Amazon marketplaces. Do NOT enable Expanded Distribution. Don’t press Publish yet.
  • Set up IngramSpark to populate everything else. Don’t press Publish yet.
  • When you’ve got both platforms set up, go back and press Publish on KDP, then press Publish on IngramSpark.

If you publish via IngramSpark first, the data feed can actually populate Amazon, so you end up selling the IngramSpark version of the book rather than the KDP version, thus negating the whole algorithm strategy (presumably).

I will add a caveat: I have experienced this issue with publishing in the “wrong” order, and I’ve talked to other authors who have run into this problem. In working with KDP and IngramSpark to try to resolve version issues in the listing, neither has been helpful; each pointed at the other as the party responsible for fixing the issue. But it’s possible they will resolve this issue systemically (or have resolved it), so at some point the order in which you publish may not matter.

How do ISBNs apply to a series of books?

Say you have a series of books–it could be a fiction trilogy or a series of related nonfiction books. How do ISBNs apply to the set?

  • Each book needs its own ISBN, as described above.
  • If you package multiple books into a box set, the set itself needs an ISBN. (The individual books already have their own ISBNs.)
  • Depending on the type of series, you may also want an ISSN (International Standard Series Number), available from the Library of Congress. They are most commonly assigned to magazines, journals, and other types of continuing publications. The acronym is similar but an ISSN is a different thing, so read more on the LOC ISSN site.

The Bowker FAQ page is useful for more on series and packages.

Still have questions?

ISBNs are a surprisingly confusing topic. If you’ve still got questions, send me an email, and I will do my best to answer or point you to another resource, and I’ll update the comments with the information. (I turned off comments after getting tired of managing spam.)

And don’t miss these related articles:

KDP vs. IngramSpark: Which Publishing Platform Is Right for You?

KDP and IngramSpark Printing Options