Comparison of Dewey and Library of Congress subject classification

This is a conversion chart showing how the Dewey Decimal and Library of Congress Classification systems organize resources by concept, in part for the purpose of assigning call numbers. These two systems account for over 95% of the classification in United States libraries, and are used widely around the world.

The chart includes all ninety-nine second level (two-digit) DDC classes (040 is not assigned), and should include all second level (two-digit) LCC classes. Where a class in one system maps to several classes in other system, it will be listed multiple times (e.g. DDC class 551).

Additional information on these classification plans is available at: