Planetary Gear Calculator

Epicyclic (planetary) gear calculator for sun, planet, and ring teeth, drive-mode ratio, RPM, and torque.

Planetary Gear Calculator sizes a single-stage sun–planet–ring set. Enter tooth counts and planet number, pick the fixed, input, and output members, and read ratio, output RPM, and output torque. A scaled drawing animates the gearset so you can check mesh, spacing, and motion before you cut teeth or print parts.

RATIO, GEOMETRY & DRIVE MODES
• Transmission ratio (ω_in / ω_out) for each drive mode
• Output RPM and torque from input speed, torque, and efficiency
• Reducer, overdrive, reverse, or 1:1 character of the selected mode
• Pitch diameters and sun–planet center distance from module or diametral pitch
• Mesh, equal planet spacing, and tip-clearance checks
• Lock any two members’ teeth and solve the third

WHO IT IS FOR
• Engineers laying out a compact coaxial reduction or overdrive
• Students and labs learning Willis / epicyclic drive modes
• Hobby and 3D-print builders checking that a sun–planet–ring set actually meshes

WHY THIS PLANETARY CALCULATOR
People look up a planetary gear calculator, epicyclic gear calculator, or sun-and-planet gear ratio tool for the same job: three members, one carrier, a usable ratio.
• Live planetary visualization with animation
• Saved setups to reuse later
• Display precision you control
• Runs on the device — works offline
• One-time purchase — no ads, no subscription

From Engineering Kit, publisher of Belt & Pulley Calculator, Chain & Sprocket Calculator, and other mechanism tools.

This app models a simple single-stage planetary (epicyclic) gearset. It is not an ISO/AGMA strength rating, a multi-stage gearbox designer, or a compound-planet catalog.