LC Call Numbers

Library materials are shelved alphabetically and numerically depending on their call numbers, which are determined by the item’s subjects. Knowing the classification letter(s) for your subject area can help you locate materials on specific and related subjects, as well as browse the shelves for related materials.

For an overview of the Library of Congress classification system, see the Wikipedia article on Library of Congress Classification.

Formats Used to Write Call Numbers

Call numbers on library materials and in the catalog appear in two formats and are read from top to bottom or left to right, as shown below:

Stacked on the book spine
Z
678.9
H9
1987

In a single line in the online catalog record
Z678.9 H9 1987

How to Read Call Numbers

When reading call numbers, consider each segment before moving on to the next segment. This process is illustrated in the following tables, which explain and give examples of the segments in Library of Congress call numbers. In each row, call numbers are arranged in correct shelf order to show how they would be arranged on library shelves. Bold type indicates the portion of the call number being discussed.

Letters comprise the first segment and indicate an item’s subject and sub-subject. The library’s arrangement is based on these letters, so it’s primarily alphabetic.

H

41
E561

HA

17
K4
1971

HB

34
N6
1990

HC

240
C518
2000

Numbers comprise the next segment and more specifically indicate subject. Read these numbers as whole numbers. If this component contains a period and another number (ie, 674.7 and 678.93), read it like you would a whole number with a decimal.

665

M672
1984

674

K35

674.7

L52
1990

678.93

M53
A54
1987

Letters and numbers comprise the next segment and indicate an author’s last name, a subject subdivision, or sometimes, a title. Read the letters alphabetically.

KF
387