About converting between ISBN-10 and ISBN-13 ISBN (International Standard Book Number) is an internationally standardized identification number assigned to publications such as books and magazines. The old format of ISBN was 10 digits (ISBN-10), but since 2007, the new format of 13 digits (ISBN-13) has become the mainstream. In the ISBN converter, you can convert between ISBN-10 and ISBN-13. The entered ISBN can be either 10 or 13 digits and may or may not contain hyphens. Conversion from ISBN-10 to ISBN-13 We will extract the first 9 digits from ISBN-10 We will add '978' at the beginning We will calculate and add the check digit for the new 13-digit ISBN Conversion from ISBN-13 to ISBN-10 Removing the prefix '978' and the trailing check digit from ISBN-13 Calculating a new check digit for the remaining 9 digits and adding it