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Understanding Library of Congress Call Numbers


After reading this sheet, try the call number practice at the end.

A call number is the address of a book or a periodical (magazine or journal) in the library. Our library uses the Library of Congress call number system for arranging most of our materials. In our library

Library of Congress call numbers are related to the main subject of a book or periodical. You may use the Library of Congress Classification to browse by subject. Here are some samples:

BF
173
H333
2006

 
LB
3013.4
G55
1990

 
ND
553
P5
A66
2002
PS
1331
E48
2000

 
QE
363.2
N48
2000

 
TK
5105.875
I57
O35
2005
a book about Jungian psychology a book about school social work a book about Picasso's painting a book about Mark Twain a book about mineralogy a book about the Internet

How to read a call number

  1. The first line of a call number may begin with one, two, or three letters. Read these letters alphabetically. A call number that begins with A is shelved before one that begins with B, C, etc.; a call number that begins with QE is located before one that starts with QL.
    QE  
        

     
    before
    QL  
        

     

  2. The second line of a call number is a number that may have one or more digits. Read this line numerically.
    HD
    987  

     
    before
    HD
    1001

     

  3. The third line is the trickiest part of the call number: The letters are shelved alphabetically, and the numbers following the letters are treated as if they were preceded by a decimal.. Thus:
    QE
    352
    C444
    1999
    before
    QE
    352
    C64
    1999
    before
    QE
    352
    C7
    1999
    before
    QE
    352
    C754
    1999
  4. This makes sense if you read the numbers as decimals!

    0.444 
    before
    0.64  
    before
    0.7   
    before
    0.754  

  5. The final lines of the call numbers may include dates, volume or issue numbers, copy numbers, and other annotations, such as "supplement". Read these annotations after the rest of the call number.

Call Number Practice

Try this exercise* to see how well you understand call numbers. (*This link only works with Internet Explorer.)

If you have trouble finding an item by its call number, please ask for help from a library employee. We'll be glad to help.