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 · Z.

SunExternal gear
PlanetExternal gear
RingInternal gear

02

Configuration

The input and output must be different members.

Fixed member

03

Transmission result

Input / output

Complete the geometry to calculate the ratio.

Output speed
Direction
Sun teeth
Planet teeth
Ring teeth
Center distance
Equation used

Willis equation: s − ωc) / (ωr − ωc) = −Zr / Zs

04

Gear layout

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

This article is tagged:


Data protection policy

Dipl.-Ing. Thomas Spielauer, Wien (webcomplainsQu98equt9ewh@tspi.at)

This webpage is also available via TOR at http://rh6v563nt2dnxd5h2vhhqkudmyvjaevgiv77c62xflas52d5omtkxuid.onion/

Valid HTML 4.01 Strict Powered by FreeBSD IPv6 support