Understanding Call Numbers

What are call numbers for?

Each non-fiction book in the library has a call number. A call number is like an address: it tells us where the book is located in the library.  Call numbers appear 

Call numbers 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. 

Most public libraries use The Dewey Decimal System. This system uses a three digit number, that can be followed by a period (referred to by library staff as "point") and up to 5 more numbers. After the numbers, there is usually one or more letters.

Reading Call Numbers

Read call numbers

Putting Call Numbers in Shelf Order

To understand how call numbers are put in order in the Dewey Decimal System, again look at each section of the call number. The first three digits indicate the subjet and are shelved first by this number. The number after the decimal point indicates a sub-category within the subject. If there is more than one number after the decimal point, it is treated as a further refinement of the subject. The letter or letters indicate the author's last name and help to further order books on the same subject.

Different call numbers in order

What does the call number mean?

Remember that Dewey Decimal System arranges materials by subjects. The first section of the call number represent the subject of the book. The numbers after the decimal point further break down the subject into regions, time periods or specific areas of study within the subject. The letter designation at the end indictates the author's last name. Note: more than one book on a subject can have the exact same Dewey Decimal number.  For example:

Lines of call number and explanation

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 523.43, there are several books on the planet Mars.

Similar books shelved together

Since the Dewey Decimal System arranges materials by subjects, knowing the first three numbers for your subject area gives you a place to start browsing the shelves.