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ISBNs part 2: Lucky number 13

Many literary geniuses would confess numbers are not their strong point.

But when publishing your book, there’s one number you’ll need to get your head around – the ISBN.

Don’t worry, it’s not complicated. There are just a couple of key things you need to know.


Recently we published an article about ISBNs which you can read here.

But one question we didn’t answer was the difference between a 10 digit and 13 digit ISBN number. It’s a question our clients often ask us, so we thought we would explain it in more detail.

Since 1970, all books have been assigned a 10 digit unique reference number – the ISBN. This stands for International Standard Book Number.

Before this, ISBNs didn’t exist. But it was becoming difficult to know if the book you were looking for was the right one. Remember, these were the days before the internet. And with all the different formats available – hardback, paperback, first edition, second edition, etc – keeping track of them all was starting to cause problems.

So the ISBN was introduced, and this gave every title, edition and format a unique number. This number was 10 digits long.

Up until 2007, the 10 digit number was sufficient, but from 1st January 2007, the publishing industry started using 13 digit ISBNs as well.

The reasons for introducing a 13 digit identifier were twofold:

1. To align the numbers with other globally used numbering systems.

To create a 13 digit number, the numbers 978 were added to the start of the 10 digit ISBN. The numbers 978 were chosen because they were already used on books as part of the barcode.

Therefore all books with a barcode also carried the 13 digit identifier, even though it was not originally intended in this way.

2. To increase the number of ISBNs available to use.

Of course, just adding 978 to each ISBN, doesn’t mean more numbers are created, but it allows for new prefixes to be created to expand the ISBN pool.

Once the 978 pool has been exhausted, the prefix 979 will be used. The 979 prefix ISBNs will NOT have a corresponding 10 digit ISBN.

Can I convert my 10 digit ISBN to a 13 digit ISBN?

Yes, the easiest way is to use the converter on Bowker’s (the official source for ISBNs in the United States) website:

You can add 978 to your 10 digit number, but the last digit may change. The last digit becomes a check digit, to check for typographical errors when entering the number. A complex formula is used to calculate the last ‘check’ digit, so it’s easiest to use the online calculator.

Do I need to show both ISBNs on my book if I have both a 10 and 13 digit ISBN?

Most publishers print both ISBNs on the Title Verso page or copyright page, for those who may still be using the 10 digit numbers.

To use both, print the numbers in this format:
ISBN-10: 1-23456-789-0
ISBN-13: 978-1-23456-789-0

Once the 979 ISBNs come into use, you will only need to print this on your book.

Have you discovered any inside knowledge about the perplexing world of ISBNs? Leave your answers in the comments section below.




We’re Peter and Caroline O’Connor. Creating beautiful book cover designs for authors all over the world is our passion. Every author should be able to benefit from a beautiful book cover design (not just the lucky few who get signed by a big publisher). We design, podcast, and coach authors full-time so we understand your struggles. Currently accepting new clients.