Learn More

Planetary Gear Set Calculator

Planetary Gear Set Calculator

Planetary (epicyclic) gear systems provide high power density and versatile gear ratios in a compact space. By varying which component is held stationary—the Sun, the Ring, or the Planet Carrier—different mechanical advantages can be achieved. This tool helps you calculate the gear ratios and verify the assembly conditions for your planetary gear set.

Determine Epicyclic Ratios

Ratio (Sun Input, Ring Fixed)
— :1
Ratio (Sun Input, Carrier Fixed)
— :1
Assembly Condition
—

Expert Protocol

The tactical roadmap.

Optimized sequence.

How It Works

A standard planetary set consists of a central Sun gear, multiple Planet gears, and an outer Ring gear. The fundamental relationship for tooth counts is Nr = Ns + 2*Np. If this isn't met, the gears will not mesh correctly.

The Formula

Gear Ratios (R):

  • Carrier Output: R = 1 + (Nr / Ns)
  • Ring Output: R = - (Nr / Ns)
  • Assembly: (Ns + Nr) / Number of Planets must be an integer.

FAQ

Can I have any number of planets?
No, the number of planets is limited by the physical space and the assembly condition (Ns + Nr) / N_planets.