Machine design tool · V0.8

Spur Gear Pair Calculator

Calculate ratio, output speed, pitch diameters, center distance, circular pitch and base diameters for a basic external spur-gear pair.

Two external spur gears showing tooth counts, pitch diameters and center distance

Pinion teeth z₁

Gear teeth z₂

Module m (mm)

Pressure angle α (deg)

Input speed n₁ (rpm)

Input torque T₁ (N·m)

Ratio i = z₂/z₁—

Output speed—

Pitch diameters—

Center distance—

Circular pitch—

Base diameters—

Ideal output torque—

d = mz · i = z₂/z₁ = n₁/n₂ · a = (d₁+d₂)/2

Basic external spur-gear geometry only. It does not size tooth strength or account for backlash, profile shift, helix angle, quality grade, contact ratio, efficiency, noise, lubrication or standards-based rating.