If you’ve check-out a book at a library, you are familiar with an ISBN. But what exactly does ISBN mean and what are its elements? 


ISBN is an acronym that stands for International Standard Book Number. According to the International ISBN Agency, it is a unique product identifier used by publishers, booksellers, libraries, retailers, and other supply chain participants for ordering, listing, sales records, and stock control purposes. An ISBN is assigned to text-based monographic publications and is always applied for by the publisher. The number is always placed on the copyright page of the book, as wells as on the back cover if there is a bar code. Every book format (paperback, hardcover, ebook) has its own ISBN, and once assigned to the product, the ISBN can never be reused. 


An ISBN is a 13 digit number (10 digits prior to 2007). It is calculated using a mathematical formula and includes a check digit to validate the number. It consists of 5 elements that are separated by spaces or hyphens.


  • 3 digits 
  • can currently only be 978 or 979 

Registration Group:

  • up to 5 digits 
  • identifies the particular country, geographical region, or language area participating in the ISBN system


  • up to 7 digits 
  • identifies the particular publisher or imprint


  • up to 6 digits 
  • identifies the particular edition and format of a specific title

Check Digit:

  • final single digit
  • mathematically validates the rest of the number

Having an ISBN is paramount when publishing a book. It increases the chances that your book will be found and allows bookstores to sell it. 

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