ISBN for books: do you need one, and how do you get it?
An ISBN (International Standard Book Number) is the 13-digit number that identifies one edition of a book, so shops, libraries and distributors can order the right one. Each format needs its own: the paperback, the hardback and the eBook are separate editions.
- Need one: for any printed book sold through shops, libraries or distributors.
- May not: for a Kindle-only eBook, which Amazon identifies with its own ASIN.
- Comes from: your national agency (Bowker in the US), in your name or your imprint's.
The short answer: if you are printing physical books you need an ISBN. If you are publishing only a Kindle eBook, you do not.
That single distinction causes more confusion than any other part of self-publishing, because Amazon identifies every product with its own ASIN, which looks like an ISBN but is not one. This page explains what an ISBN does, when it is required, who owns it, and what goes wrong when one is assigned incorrectly.
What an ISBN actually is
An ISBN, or International Standard Book Number, is a thirteen-digit identifier for one edition of one book in one format. It is how the book trade finds a specific product: when a bookshop orders a title, or a library catalogues one, the ISBN is what identifies it precisely.
Three consequences follow, and they surprise people:
- One edition, one number. A paperback and a hardcover of the same book need separate ISBNs. So does a revised edition where the content has substantially changed.
- It is not a licence. An ISBN does not grant rights, take rights, or restrict you to one printer or retailer. It is an identifier, nothing more.
- It never expires. Once registered, the ISBN belongs to that edition permanently. It cannot be unassigned or recycled.
ISBN-10 vs ISBN-13: which one do you need?
You need the ISBN-13. Since 1 January 2007 every new ISBN has been thirteen digits, and the barcode on the back cover is built from the ISBN-13. The ten-digit ISBN-10 is the older format. You will still see it on books published before 2007 and in some catalogues, and it is the same book under an older number.
| ISBN-10 | ISBN-13 | |
|---|---|---|
| Digits | 10 | 13 |
| In use | Until 2006 | From 1 January 2007 |
| Starts with | Group digit (0 or 1 for English-language books) | 978 or 979 |
| Last digit | Check digit, can be an X | Check digit, always a number |
| Barcode | Not used directly | Printed as the EAN-13 barcode |
How to convert an ISBN-10 to an ISBN-13:
- Drop the last digit of the ISBN-10. It was only the check digit.
- Put 978 in front of the remaining nine digits.
- Work out the new check digit: multiply the twelve digits alternately by 1 and 3, starting with 1, and add them up. The check digit is the number that brings the total up to the next multiple of 10 (0 if it is already one).
Worked example: 0-306-40615-2 becomes 978-0-306-40615, and the twelve digits add up to 93 with the 1 and 3 weights, so the check digit is 7. The ISBN-13 is 978-0-306-40615-7. The 978 prefix is the one most books carry. 979 numbers exist as well and have no ISBN-10 equivalent, so a 979 ISBN cannot be converted back.
ISBN or ASIN? The rule that decides it
| Situation | What you need |
|---|---|
| Kindle eBook on Amazon only | ASIN — no ISBN required |
| eBook sold outside Amazon too | ISBN recommended for non-Amazon channels |
| Paperback or hardcover, print on demand | ISBN required |
| Printed books sold in shops or to libraries | ISBN and printed barcode required |
An ASIN is Amazon's internal product identifier. Every item on Amazon has one, including things that are not books. It is useful and sufficient inside Amazon, and it is why many authors publishing only an eBook never need an ISBN at all. The moment a physical edition exists, the ISBN becomes necessary, because the rest of the trade does not use ASINs.
Who is the publisher of record?
When an ISBN is registered, a publisher is named. That name appears in trade databases and is the publisher of record for the title. If an author registers through their own imprint, the imprint is the publisher of record.
If we register on an author's behalf, the ISBN goes in the author's own name or their own imprint — never in ours. You are the publisher of record, and you keep the rights to your book. The registration is a service, not a claim on the title.
Decide on the imprint name before registration. Changing the publisher of record afterwards means re-registering, and in most cases a new number.
The barcode block
An ISBN only works in retail if it is printed as a scannable barcode on the back cover. That element is called the barcode block, and it has hard requirements:
- Pure black bars on a white background — no colour, no grey, no tint
- A white quiet zone around the barcode, so scanners can read the edges
- Printed at a scannable size, with the number legible beneath
- Vector artwork, or a raster image at high enough resolution for print
A barcode that looks fine on screen can still fail scanning when printed. This is one of the most common reasons a print file is rejected by a retail platform, and it is worth checking against the platform's specification before you upload.
Why an ISBN gets rejected as already registered
This is a specific problem with bulk allocations, and it is more common than authors expect.
National agencies issue ISBNs in blocks — often ten or more at a time. To register a block, the applicant supplies a list of titles. In practice, some of those titles are placeholders rather than real books, because the block is being claimed before the books exist.
The consequence: a number that looks unused on your list is already registered against whatever title was named at the time. When you assign it to a different book and submit it, the platform rejects it, because the ISBN already belongs to another title.
The lesson is to reconcile the block before assigning anything. Check every number in the block against what was registered against it, and establish which are genuinely free. Assigning from a list without doing that is how numbers end up on the wrong books — and once a barcode is printed, the error is in the physical product.
Where ISBNs come from and what they cost
ISBNs are issued by the national agency for your country. Current indicative pricing:
| Agency | Coverage | Indicative cost |
|---|---|---|
| Bowker | United States | Single ~$125 · block of 10 ~$295 |
Buying a block of ten is usually better value than buying singly if you plan more than one title, or expect revised editions. Fees change, so we confirm the current charge before registering rather than quoting from memory.
The price in the barcode (EAN-5)
A book barcode can carry a second, five-digit add-on, the EAN-5, that encodes the recommended retail price. It is the small extra block you see to the right of the main barcode on many trade paperbacks, and it lets a shop's scanner read the price from the cover.
- It is optional. Many self-published books leave it out and sell perfectly well.
- It matters mainly in physical shops, where a fixed cover price helps the retailer. For books sold only online it matters much less.
- It must match the price the book is sold at, so a price change means a new barcode. The code "90000" means no price is set.
- The first digit sets the currency (5 for US dollars), so a book sold in several countries usually leaves the price out.
How to get an ISBN: US, UK, Canada, Australia
Each country has its own agency, and you get the ISBN from the agency for the country where you are the publisher, not where the book is printed:
| Country | Agency | Note |
|---|---|---|
| United States | Bowker | Sold singly or in blocks; a block is cheaper per number |
| United Kingdom | Nielsen | The UK ISBN agency |
| Canada | Library and Archives Canada | Free to Canadian publishers |
| Australia | Thorpe-Bowker | The Australian ISBN agency |
| Nigeria | National Library of Nigeria | The Nigerian ISBN agency |
Every one of our publishing packagesincludes the ISBN, registered in your name or your imprint's, so you are the publisher of record.
Related: ISBNs and barcodes for children's books and eBook conversion.
Frequently asked questions
Do I need an ISBN for my book?
It depends on the format. If you are publishing only an eBook through Amazon KDP, your title is identified by an ASIN and you do not need an ISBN. If you are printing physical books, you need an ISBN, because bookshops, libraries and distributors identify print editions by ISBN.
What is the difference between an ISBN and an ASIN?
An ASIN is Amazon's own product identifier and applies to anything sold on Amazon, including Kindle eBooks. An ISBN is the international standard book number used across the whole book trade. A print book needs an ISBN. A Kindle-only eBook does not, though you can assign one if you want it listed outside Amazon.
What is the difference between ISBN-10 and ISBN-13?
ISBN-10 is the older ten-digit format, used until the end of 2006. ISBN-13 has been the standard since 1 January 2007: thirteen digits starting with 978 or 979, and the number your barcode is built from. Any new book needs an ISBN-13. To convert an ISBN-10, drop its check digit, put 978 in front and work out a new check digit.
Can two books share an ISBN?
No. One ISBN identifies one edition of one title in one format. A paperback and a hardcover of the same book need separate ISBNs, and so does a revised edition with substantially changed content.
Who is the publisher of record on my ISBN?
Whoever is named as the publisher when the ISBN is registered. If we register it on your behalf, it is registered in your name or your imprint's name, and you are the publisher of record. You keep the rights to the title.
Can I use my own imprint name?
Yes. If you have established, or want to establish, your own publishing imprint, the ISBN can be registered under that name. Tell us the imprint name before registration, because changing the publisher of record afterwards requires a re-registration.
Does getting an ISBN through you stop me selling elsewhere?
No. An ISBN is non-exclusive. It does not restrict you to one printer, retailer or platform. The same ISBN can be used for your Amazon listing, your own website, bookshops and any other outlet selling that edition.
Why was my ISBN rejected as already registered?
This happens when a number has already been registered to another title. It is common with bulk ISBN allocations, where an agency issues a run of numbers against a list of titles and some of those titles are placeholders. If one of the placeholder numbers is later assigned to a different book, the platform rejects it, because the number belongs to the title on the original registration.
What is a barcode block and why does it matter?
A barcode block is the printed EAN-13 barcode, derived from the ISBN, placed on the back cover with a white quiet zone around it. Retailers and distributors scan it, so a missing, malformed, or wrongly-scaled barcode can stop a book being listed or sold in shops. The barcode must be pure black on a white background at sufficient resolution.
Where do ISBNs come from?
ISBNs are issued by the national ISBN agency for your country. In the United States it is Bowker. Agencies issue numbers individually or as blocks of ten or more.
How much does an ISBN cost?
It varies by agency and by whether you buy one number or a block. In the United States, Bowker sells a single ISBN for around $125 and a block of ten for around $295, which is why buying a block is common for authors publishing several titles. Costs and availability change, so we confirm the current fee before registering.
How do I register my ISBN?
Buying the number from your national agency is what assigns it to you. You then attach the book's details to that number: title, author, publisher or imprint name, format and binding, language and publication date. You need a separate ISBN for each edition, so the paperback, the hardcover and the eBook (if you want one) each get their own. We can buy and register the ISBN in your name or your imprint's name as part of publishing your book, so you are the publisher of record.
What do I need to get an ISBN?
You need the book's title and subtitle exactly as they appear on the cover, the author name, the name of the publisher or imprint you want on the record, the format and binding, the language and the planned publication date. Have these settled first, because the publisher of record is hard to change after registration.
How long does it take to get an ISBN?
It depends on the agency. Some issue the number as soon as you buy it, others take days or longer, so order it before your cover and interior are final. The ISBN has to be on the copyright page and in the barcode on the back cover before the book is printed.
Can I sell my book without an ISBN?
Yes, in some cases. A Kindle-only eBook on Amazon is identified by its ASIN, and you can sell printed copies yourself without one. But bookshops, libraries and distributors identify a print book by its ISBN and will not stock it without one.
Can I self-publish my book and get an ISBN?
Yes. You can buy your own ISBN, or have it bought for you in your name as part of a publishing package. Some platforms, such as Amazon KDP, offer a free ISBN, but then the platform is the publisher of record and that number can only be used with them. If you want to publish across several stores or keep the imprint name yours, use your own ISBN.
Can I put the price in my book's barcode?
Yes, with the optional five-digit EAN-5 add-on beside the main barcode. It is useful for books sold in physical shops at a fixed price, but it must match the price the book is actually sold at, so many self-published authors leave it out.
Do I need a separate ISBN for each format?
Yes. The paperback, the hardback and the eBook are separate editions, and each needs its own ISBN. A Kindle-only eBook can use Amazon's ASIN instead, but an eBook sold through other stores needs its own ISBN.
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