Understanding Call Numbers

Have you ever wondered how library books are assigned their places on the shelves? Did you know that the call number -- the number placed on the spine of the book -- is a code which provides valuable information about the book? This is an introduction to understanding and using Library of Congress call numbers.

What is the purpose of call numbers?

Each book in the library has a unique call number. A call number is like an address: it tells us where the book is located in the library.

Call numbers appear

on the spines of books and in the online catalog

Note that the same call number can be written from top-to-bottom, or left-to-right.

Ingram Library uses Library of Congress Classification for call numbers. This system uses a combination of letters and numbers to arrange materials by subjects.

How do you read call numbers?

Read call numbers line by line

In what order do call numbers appear on the shelf?

To understand how call numbers are put in order in Library of Congress Classification, look again at each section of the call number.

Call number

Here is the same list of call numbers as in the above diagram, with explanations of how they were put in order:

  1. LA2301 .M37
  2. LB2327 .M3 (LB comes after LA)
  3. LB2327 .V53 1990 (Both start with LB2327, V comes after M)
  4. LB2328 .B37 (2328 comes after 2327)
  5. LB2328 .C34 (C comes after B)
  6. LB2328 .C55 (Both start with LB2328 .C, decimal .55 comes after .34)
  7. LB2328 .C554 1982 (Decimal .554 comes after .55)
  8. LB2395 .C65 1987
  9. LB2395 .C65 1991 (Same call numbers except for date: 1991 comes after 1987)

What information does the call number tell you?

The Library of Congress Classification system arranges materials by subject. The first sections of the call number represent the subject. The letter-and-decimal section of the call number often represents the author's last name. The last section of a call number is often the date of publication.


call number information

Why is this important to know?

Because books are classified by subject, you can often find several helpful books on the same shelf, or nearby. For example, within the same call number LB2395, there are other guides for college study.

call number classification


Acknowledgement: Thanks to Honolulu Community College Library.
Page used and adapted with permission.