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The International Standard Book Number (ISBN) is a unique identifier for books, crucial for their distribution and sales. In 2007, the ISBN system transitioned from a 10-digit format to a 13-digit format. This change was made to align with the European Article Number (EAN), a universal product code for books. Let’s delve into the structure of a 13-digit ISBN and understand its components.

For a comprehensive understanding of the following content, it might be beneficial to have prior knowledge of the 10-digit ISBN, as the 13-digit ISBN evolved from it. For more information on the 10-digit ISBN, please refer to the Anatomy of a 10-digit ISBN page.

The Five Parts of a 13-Digit ISBN

A 13-digit ISBN is divided into five parts:

  1. Prefix: The current prefix is either 978 or 979. This prefix aligns the ISBN with the EAN system.
  2. Registration Group Identifier: This part of the ISBN identifies a country, geographical area, or language area participating in the ISBN system. It can consist of up to five digits, allocated by the International ISBN Agency.
  3. Registrant Element: This element signifies the publisher that published the book bearing that ISBN. It can consist of up to seven digits, allocated by the publisher’s ISBN agency for the group (the country, geographical area, or language area) in which it falls.
  4. Publication Element: This part of the ISBN identifies the specific edition of the book allocated an ISBN. It can consist of up to six digits. The publication element is also used to pad, if necessary, the length of the ISBN to 13 digits, by having preceding zeroes added to it.
  5. Check Digit: The check digit is the last digit of the ISBN. Its value is calculated from the other twelve digits of the ISBN and provides a check on the validity of the ISBN. If a mistake is made in transcribing the ISBN, such as a wrong number or a transposition error, the resulting ISBN will likely be invalid, indicating the error.

Calculating the Check Digit

The check digit is calculated using a numerical equation involving the first twelve digits of the ISBN. The calculation involves a modulo 10 system where the first digit is multiplied by 1, the second by 3, the third by 1, the fourth by 3, and so on. All solutions are then added together, and the check digit is added last to make the total a multiple of 10. This process is called the modulus 11.

Similar to the 10-digit ISBN calculation where 11 was used, the resulting number is reduced by 10 as many times as possible, leaving a remainder between 0 and 9. If the remainder is 0, then the check digit is also 0. If not, the check digit is determined by subtracting the remainder from 10.

The calculation for the example book, with the first four sections of its ISBN being 978059652068, is demonstrated below.

ISBN without check digit: 978-0-596-52068-check digit or 9,7,8,0,5,9,6,5,2,0,6,8,check digit
Weight: 1,3,1,3,1,3,1,3,1,3,1,3

ISBN Digit978059652068
Weight131313131313
Multiply (Digit X Weight)9218052761520624

Sum: 9 + 21 + 8 + 0 + 5 + 27 + 6 + 15 + 2 + 0 + 6 + 24 = 123

123 divided by 10 = 12 remainder 3
The check digit is 10 – 3 = 7

Validating the Check Digit

A complete ISBN, including its check digit, can be validated by a similar procedure to calculating the check digit. The same calculation is performed, adding the check digit to the calculated product with a weighting of one. If the check digit should be the letter X, then it takes the value of 10. When the division by eleven is performed, the remainder will be zero for a valid ISBN.

ISBN without check digit: 978-0-596-52068-7 or 9,7,8,0,5,9,6,5,2,0,6,8,7
Weight: 1,3,1,3,1,3,1,3,1,3,1,3,1

ISBN Digit9780596520687
Weight1313131313131
Multiply (Digit X Weight)92180527615206247

Sum: 9 + 21 + 8 + 0 + 5 + 27 + 6 + 15 + 2 + 0 + 6 + 24 + 7 = 130

130 divided by 10 = 13 remainder 0
Zero remainder = valid ISBN

Final Thought

The ISBN does not provide any form of legal or copyright protection. However, it is a crucial identifier for publishers, bookstores, libraries, and more, playing a significant role in ordering, sales reporting, and inventory control. An ISBN increases the chances that your book will be found and is legally required to identify publications in some countries.

The 13-digit ISBN emerged from the restructuring brought about by the fourth edition of the ISO 2108 standard, which outlines the ISBN system. This revision primarily ensures the availability of new ISBNs for the foreseeable future. Additionally, it incorporates the ISBN system into the broader EAN product numbering system, which also utilizes 13 digits for a wide variety of goods.

Understanding the anatomy of a 13-digit ISBN is essential for anyone involved in the publishing process. It ensures the correct identification of a book and its specific edition, facilitating efficient distribution and sales.