What Is Gear Module?
Gear module (abbreviated as m) is the fundamental unit used in the metric gear system to define the size of gear teeth. It is defined as the ratio of the pitch diameter to the number of teeth:
m = d / z
Where d is the pitch diameter (mm) and z is the number of teeth.
Why Module Matters
Module is the most important parameter when selecting metric gears. Two gears can only mesh together if they have the same module and the same pressure angle. KHK USA stocks gears from Module 0.5 through Module 14 — covering virtually every industrial application.
Module vs. Diametral Pitch
In the inch system, gear size is defined by Diametral Pitch (DP), which is the inverse of module. The relationship is:
DP = 25.4 / m
For example, Module 1 corresponds to approximately 25.4 DP. KHK USA’s Module ↔ DP Converter tool makes this conversion easy.
Common Module Sizes
The most commonly used modules in industrial applications are: 0.5, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 8.0, 10.0, 12.0, and 14.0. KHK USA maintains stock inventory across all standard modules for same-day or 3-day USA delivery.
How to Select the Right Module
Module selection depends primarily on the transmitted load and gear geometry constraints. Larger modules produce stronger teeth but require larger center distances. As a starting point, calculate the required module using Lewis bending stress analysis — KHK USA’s Gear Torque Calculator handles this automatically.