What Is a Cutter Number? A Plain-English Guide for Librarians

A Cutter number is the short author code that follows a classification number on a spine label. It is what keeps two books on the same topic in a predictable, alphabetical order on the shelf. If you have ever seen a label like 813.54 F553g, the F553g part is the Cutter number.

Why Cutter numbers exist

Classification numbers (Dewey or Library of Congress) group books by subject. But dozens of books can share the same subject number. The Cutter number adds a second layer of sorting — by author surname — so every book lands in exactly one spot and is easy to find again.

How a Cutter number is built

• First letter: the capital first letter of the author's surname (Fitzgerald → F).
• Numeric portion: the next letters are converted to numbers using a Cutter table, producing something like 553.
• Work mark: a lowercase letter from the title distinguishes multiple books by the same author (Gatsby → g).

Combined, Fitzgerald's The Great Gatsby becomes a Cutter like F553g.

A worked example

Say you are cataloging Beloved by Toni Morrison, classified at 813.54:

• Surname Morrison → M
• Cutter table converts "orrison" → 677
• Title Beloved → work mark b

Final call number: 813.54 M677b.

Keeping Cutter numbers consistent

The single most important rule: the same author should always produce the same Cutter. Inconsistency is what makes shelves drift out of order over time. This is exactly where manual cataloging breaks down in small libraries with rotating volunteers.