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How to read a Library of Congress call number

The Undergraduate uses the Library of Congress (LC) Classification to organize its books. Most other libraries, including the Main Stacks, continue to be organized using Dewey Decimal. You will find information that will help you understand LC call numbers below.

How do I know if I have an LC or Dewey call number?

The easiest way to tell whether a call number is LC or Dewey is to look at the beginning of the call number.

You can find a guide to reading Dewey Decimal call numbers here.

How are LC call numbers organized?

Like with Dewey, the LC classification system groups together books on similar subjects by means of their call numbers.

There are 21 main LC call number classifications or classes:

A General Works
B Philosophy, Psychology, Religion
C Auxiliary Sciences of History
D World History and History of Europe
E History of the Americas
F History of the Americas
G Geography, Anthropology, Recreation
H Social Sciences
J Political Science
K Law
L Education
M Music
N Fine Arts
P Language and Literature
Q Science
R Medicine
S Agriculture
T Technology
U Military Science
V Naval Science
Z Bibliography, Library Science, Information Resources

Within each of these larger classes are subclasses that are indicated when the call number begins with two or more letters.

To see the subclasses located under each main class, see the Library of Congress Classification Outline. Click on a class to view its subclasses.

Making sense of a call number

Here is a sample Library of Congress call number:

Z66 2010

Zombies, Vampires, and Philosophy: New Life for the Undead, edited by Richard Greene and K. Silem Mohammed


Philosophy, Psychology, Religion




Occult Sciences


Demonology, Satanism, Possession


Zombies, Vampires, and Philosophy: New Life for the Undead

Each LC call number begins with one to three letters and is followed by a series of numbers. LC call numbers are organized alphabetically, starting with the first letter on the left. They are subsequently organized numerically according to the numbers that follow.

How do I read an LC call number?

How do I find LC call numbers on the shelf?

Follow this example to see the order in which books will appear on the shelf.

LC call number shelf

(image courtesy Board of Regents of the University System of Georgia)