How to Find the Dewey Decimal Number for a Book

How to Find the Dewey Decimal Number for a Book

The Dewey Decimal Classification (DDC) system is a widely used method for organizing and categorizing books in libraries. Created by Melvil Dewey in 1876, it offers a systematic way to locate books based on subject areas. Understanding how to find the Dewey Decimal number for a book can greatly assist in navigating library collections and discovering relevant resources. In this article, we will explore the steps involved in finding the Dewey Decimal number and provide answers to common questions regarding this classification system.

Understanding the Dewey Decimal System

The Dewey Decimal System is divided into ten main classes, each represented by a numerical range. These classes are further divided into subdivisions, allowing for more specific categorization. The system covers a wide range of subjects, including humanities, social sciences, natural sciences, and technology.

Step 1: Determine the Subject

Before you can find the Dewey Decimal number for a book, you need to identify the subject area it belongs to. This can be done by examining the title, the author’s name, or a brief description of the content. If you are unsure about the subject, consult the library’s catalog or ask a librarian for assistance.

Step 2: Locate the Dewey Decimal Classification

Once you have determined the subject area, locate the Dewey Decimal Classification chart. This can usually be found near the library’s reference desk or on its website. The chart lists the main classes and their corresponding numerical ranges. For example, class 000-099 represents computer science, information, and general works, while class 500-599 covers natural sciences and mathematics.

Step 3: Identify the Subclass

After finding the appropriate class, look for the subclass that best matches the subject of the book. Subclasses are represented by three-digit numbers. For instance, subclass 005 pertains to computer programming, while subclass 530 is dedicated to physics. The subclass numbers are further divided into decimal fractions to provide more specific categorization.

Step 4: Locate the Book

Once you have identified the subclass, use the Dewey Decimal number to locate the book on the library shelves. Books are arranged in numerical order, with each subclass arranged in alphabetical or numerical order within its range. If you are having trouble locating a specific book, do not hesitate to seek assistance from a librarian.

Frequently Asked Questions (FAQs)

Q: What if the book covers multiple subjects?
A: In such cases, the book will be assigned multiple Dewey Decimal numbers, each representing a different subject area. It may be located in one section of the library but cross-referenced in others.

Q: How often does the Dewey Decimal system get updated?
A: The Dewey Decimal system is regularly updated to reflect changes in knowledge and the addition of new subjects. The most recent edition, Dewey Decimal Classification, 23rd edition, was published in 2011.

Q: Can I use the Dewey Decimal system to locate e-books or online resources?
A: While the Dewey Decimal system was primarily designed for physical books, some libraries have adapted it for online resources. However, online catalogs often use different systems such as Library of Congress Classification or proprietary classifications.

Q: Can I browse books in a library by Dewey Decimal number?
A: Yes, browsing books by Dewey Decimal number can be an effective way to discover new resources on a specific subject. Libraries often provide detailed maps or signage to help patrons navigate the collections.

Q: Can the Dewey Decimal system be used in all libraries?
A: The Dewey Decimal system is widely used in public, school, and small to medium-sized academic libraries. However, larger academic and research libraries often use the Library of Congress Classification system, which provides more detailed subject classifications.


Knowing how to find the Dewey Decimal number for a book is an essential skill for navigating library collections. By understanding the main classes and subclasses of the Dewey Decimal system, you can efficiently locate books and discover resources on specific subjects. Although the system may appear complex at first, with practice, it becomes a valuable tool for organizing and accessing information in libraries.

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