The form above will convert a ten-digit ISBN into its hyphenated form if possible. It will also display the EAN, or ISBN-13 and the GTIN.


The International Standard Book Number (ISBN) is a numeric commercial book identification which is intended to be unique. An ISBN is assigned to each separate edition and variation (except reprintings) of a publication. A paperback and a hardcover edition of the same book will each have a different ISBN.

The initial ISBN identification format was devised in 1967, based upon the 9-digit Standard Book Numbering (SBN) created in 1966. The 10-digit ISBN format was developed by the International Organization for Standardization (ISO) and was published in 1970 as international standard ISO 2108 (the 9-digit SBN code can be converted to a 10-digit ISBN by prefixing it with a zero digit '0').


The 10-digit ISBN is made up of four segments, and the 13-digit has a fifth, the Bookland EAN prefix. The check digits between formats do not usually match.

  1. Registration Group Identifier
  2. Registrant or Publisher Code
  3. Publication Number
  4. Check Digit


The first segment of an ISBN is the Identifier Group, and it can be from 1 to 5 digits long. It refers to either the publisher's place of business, or the language the book is written in. The single-digit identifiers are 0-5, and 7. 0 and 1 are English. 2 is French, 3 is German, 4 is Japan, and 5 is the former USSR. 7 is China.

The smaller markets share the 6, 8 and 9 spaces. There are currently more than 200 Identifier groups. There is a list of them here. Using more digits in the identifier section leaves fewer digits for the rest of the ISBN, so the markets are distributed as best they can be from 1 to 5 digits.

It is by no means uniformly distributed, and there are many exceptions necessary to fit everything in. There are large countries like Russia with no exclusive prefix at all. And there are countries that have run out of space and so need 2,3,4 or even 5 different prefixes, in the case of Mongolia. The identifier prefixes are followed by the publisher codes.


Publisher Codes are between 2 and 7 digits long, at least in the case of English identifier groups 0 and 1. This provides space for very large publishers, such as McGraw-Hill or Harper Collins, to have up to 1,000,000 unique ISBNs for their titles. For very small publishers, given a 7-digit publisher code, there is space for only 10 titles. Each digit longer the publisher code becomes reduces the total space by a factor of 10. So a 3-digit code for a publisher like MacMillan, has space for 100,000 titles.

You can look at the breakdowns and some examples for the Group 0 and Group 1 publisher codes, and you'll quickly see some limitations apparent in this system.


The Publication Code is assigned by the publisher to a particular edition of a book. Each publisher chooses how to assign these once they purchase ISBNs in blocks. Essentially this is a serial number for books within a particular publisher.

Each format of a particular work will have an individual ISBN. So an e-book, a hardcover, a paperback, and an audiobook would use four ISBNs. ISBNs a generally purchased from and issued by R. R. Bowker in the United States, and anyone can buy 1, 10, 100, or 1000 ISBNs to publishe for themselves or others.


The check digit is the last digit in an ISBN. It is used in order to validate the rest of the number. Mathematically, the ISBN must be consistent in order to be seen as valid. This is generated through a summation of multiples of the different digits and their positions in the ISBN.

The check digit is the one piece that will differ between an ISBN-10 and ISBN-13. In ISBN-10, a check digit can be 0-9 or X. In the newer barcode world, the X is eliminated, and for ISBN-13, which is part of the EAN standard, the check digit can contain only 0-9. They are calculated differently, but are used for the same function, and have no real purpose in the identity other than to avoid computer scanning or transcription errors propagating.

With new formats and ever accelerating numbers of works published, 10 (really 9 and a check digit) digits are simply not enough. In 2007, to expand the space, and to better integrate with newer UPC, EAN, and now GTIN barcodes, the 13-digit ISBN was launched. All past ISBNs were placed within the 978 'Bookland' prefix. Additionally the 979 prefix was reserved to effectively double the space of ISBNs.

The 979 space of ISBNs, though, will not be able to preserve the existing identifier and publisher codes. For one, the 979-0 space was reserved as 'Musicland' to preserve printed sheet music with ISMN numbers. So books only have 979-1 through 979-9. Further, as you can see above, many countries and languages have shifted sizes, identities, and more, and the earlier separations did not suffice for the world we see now.

The 979 prefix has no associated ISBN-10, all of the original ISBNs exist only in the 978 space. So only ISBN-13 books beginning with 978 can be converted into an ISBN-10.

There will likely be more prefixes assigned to books by the GS1 in time. And the 978 prefix is not entirely exhausted. Some publishers reuse ISBNs for out of print books instead of buying new ones. So right now, 979 is not common to see. Currently only France (10), South Korea (11), Italy (12) and The United States of American (8) have identifiers in common use.

Much of this is so much inside baseball, of course, and of interest only to archivists and collectors. For the normal person, maybe buying a book online, the takeaway is simpler. If you are intending to buy a book in English, look for a 10-digit ISBN starting with 0 or 1, or able 13-digit ISBN starting with 978-0, 978-1, or 979-8.