Dewey Decimal Classification System

How are books organized in libraries?  Not by colour. Not by size.  Not by age.   Instead, all the books in libraries are organized by topic. Over one hundred years ago, a librarian in the United States came up with a numbering system that is now used in thousands and thousands of libraries all over the world: the Dewey Decimal Classification System.

Melvil Dewey was born in in a small town in the state of New York during the winter of 1851. Even when he was young, he liked organizing things and he liked  math. While attending college, he worked in a library which he considered quite disorganized.  So, when he was 21 years old, he invented his own system for arranging books .

Here is how it works. . .

  • There are 10 main classes:

000-099  General Works including encyclopedias and computer science
100-199: Philosophy and Psychology
200-299: Religion and Mythology
300-399: Social Sciences including organization, governments and laws
400-499: Languages including dictionaries
500-599: Natural Science
600-699: Technology and Applied Science
700-799: Fine Arts and Recreation
800-899: Literature
900-999: History, Geography and Biography

  • In each class, there are 10 divisions.

500-509: General Sciences
510-519: Mathematics
520-529: Astronomy
530-539: Physics
540-549: Chemistry
550-559: Earth Sciences including Geology and Meteorology
560-569: Paleontology
570-579: Life Sciences including Ecology and Microorganisms
580-589: Plants
590-599: Zoology

900-909: General History including world exploration
910-919: Geography of the World
920-929: Biography
930-939: Ancient History
940-949: History of Europe
950-959: History of Asia
960-969: History of Africa
970-979: History of North America
980-989: History of South America
990-999: History of Other Areas including Australasia and Antarctica

  • And in each division, there are 10 sections.

910: General geography and travel
911: History of geography
912: Maps and Atlases
913: Geography of the ancient world
914: Geography of Europe
915: Geography of Asia
916: Geography of Africa
917: Geography of North America
918: Geography of South America
919: Geography of Other Areas

All the books in a library, both fiction and nonfiction, have a place in the Dewey Decimal Classification System:

  • Folklore: 398.2
  • Picture Story Books: 800s
  • Novels and Short story collections: 800s
  • Poetry: 800s
  • 800s Biographies: 920s

But most libraries take some of the books and put them in their own sections.  What does your library do?

Librarians put label on the spines of the books so that everyone knows where they belong. Here are some of the sections that might be in your library in addition to the books with Dewey numbers on the spines.

  • F = all the novels
  • E or P = all the picture books
  • B = all the biographies of individual people


Within a section of the library, most the books with the same number or letter on the top line of the spine label are arranged in order by the author’s last name.

  • Novels by Deborah Ellis: F Ell
  • Picture Books by Robert Munsch: P M

But in the biography section, books are arranged by the subject’s last name.

  • Books about explorer Henry Hudson: B Hud
  • Books about author Lucy Maud Montgomery:  F Mon

To learn more about the Dewey Decimal Classification System and to practise using this great way of finding books, play some of these games!