Skip to main content

Dewey Decimal Call Numbers

The Dewey Decimal classification system groups together books on similar subjects by means of their call numbers.


There are 10 main Dewey Decimal call number classifications or classes. 

  • 000 - Computer Science, Information, & General Works    
  • 100 - Philosophy & Psychology    
  • 200 - Religion    
  • 300 - Social Sciences    
  • 400 - Language
  • 500 - Science
  • 600 - Technology
  • 700 - Arts & Recreation
  • 800 - Literature
  • 900 - History & Geography

See where these classes are located in the University Library using our Book Location Guide.

Reading the number

ex: 305.20973 T39

First three numbers: Books are arranged sequentially. The first number of a Dewey Decimal call number indicates the general class the call number falls within. In our example, the book is located under the 300s, which is where books on social sciences are classed. If there is a second or third numbers, these indicates a specific divisions and sections. 305 indicates groups of people.


Numbers following the first 3 numbers: The numbers define the subject of the book. The number .2 is referring to a book about a specific age group and 0973 means the history and description about America.

T39 Cutter Number (the next set of numbers):  The Cutter Number indicates the author or title of the book. It is taken from a table matching names or titles to a set of numbers. In our example, T39 reflects the first word of the author, Taylor.