Planetary Gear Calculator

- tsp
Last update 12 Jun 2026
Reading time 2 mins

Simple planetary gear set

Planetary Gear Calculator

Enter any two gear sizes. The calculator completes the geometry, evaluates the selected configuration, and draws the gear set.

Zr = Zs + 2Zp

01

Gear geometry

Enter any two tooth counts. Pitch diameters use d = m Β· Z.

SunExternal gear
PlanetExternal gear
RingInternal gear

02

Configuration

The input and output must be different members.

Fixed member

03

Transmission result

Input / output β€”

Complete the geometry to calculate the ratio.

Output speedβ€”
Directionβ€”
Sun teethβ€”
Planet teethβ€”
Ring teethβ€”
Center distanceβ€”
Equation used

Willis equation: (Ο‰s βˆ’ Ο‰c) / (Ο‰r βˆ’ Ο‰c) = βˆ’Zr / Zs

04

Gear layout

Schematic pitch geometry. Tooth shapes are illustrative, not manufacturing profiles.

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