Understanding Library of Congress Call Numbers

What is a call number?

A call number is an address. It tells you where the book (or DVD or print Journal) is located within the library. A book’s call number appears in the University of Toronto Library catalogue, which you can access at the top of the UTM library website. In the library catalog, the call number is written horizontally

Catalogue record with arrows

On the book spine, it appears vertically, making it easier to find a specific call number on the shelves. Each book (or other item) has its own unique call number, which is taped to the lower outside edge of the book’s spine.

book spines with call numbers
Photo by: CCAC North Library
LC Classification Subject Divisions

A - General Works
B - Philosophy, Psychology, Religion
C – History - Civilization
D - History – General (not U.S.)
E - U.S. History
F - U.S. Local History and Latin American History
G - Geography, Anthropology, Recreation
H - Social Sciences
J - Political Science
K - Law

L - Education
M - Music
N - Fine Arts
P - Language & Literature
Q - Science
R - Medicine
S - Agriculture
T - Technology
U - Military Science
V - Naval Science
Z - Information Science

How do I browse the shelves from off campus?

The University of Toronto Library catalogue allows you to browse the shelves at all libraries or a specific library from your computer.

  1. Search for books on your topic by doing a Keyword search in the librarycatalogue.
  2. Choose a book in your results that closely matches your topic of interest.
  3. Click on its call number. You will be redirected to browse the shelves.
  4. The default for Shelf Browse allows you to wander through the books of all the libraries in the system. If you want a specific library, click on “Select specific library” and choose the library of your choice.
  5. When you click on the cover icon for a book, below it there will appear the words view details. If you click on this text, you can see the full catalogue record for an item, including which libraries own a copy and where in the library you can find the item.

How do I read a call number?

Library of Congress call numbers are arranged alphabetically and numerically. Read call numbers from left to right and from top to bottom. 

What do the numbers and letters in the call number actually mean?

LC call numbers begin with letters that represent subject divisions. Following the initial letters are numbers that help define the subject of the material.

This call number system allows materials on related subjects to be shelved in the same area. For example, if a patron goes to the book shelves to locate the call number QP376 .A4225 2009, other books on Neurophysiology will be found nearby.


Letters in the first line of the call number are shelved in alphabetical order.


The second line of a call number is shelved in numerical order.

50   55   76  76.15

The third line is the trickiest part of the call number. The letter is shelved alphabetical. The numbers, however, are shelved in decimal order as if there was an invisible decimal between the letter and the number.

QR     QR    QR   QR
450    450  450  450
.K346 .K40 .K5  .L11

The final lines of the call numbers may include dates, volume indicators, and copy numbers. These annotations are read after the call number.

QM  QM    QM    QM
10  10      10     10
C3  C3      C3     C3
      1933  1990  1996 

       c. 1

Here is an example: The lives of the brain: human evolution and the organ of mind by John S. Allen.

QP represents a specific area of science, i.e. Physiology
376 defines book as Neurophysiology
.A4225 is a code for the author's last name, i.e. Allen
2009 the year of publication

This material has been adapted from the following websites:http://www.lib.k-state.edu/help/lccn.htmlandhttp://www.ryerson.ca/library/subjects/guidecallnos.html.