From our study of normal 2-gear interactions we know that the amount of traversal is determined by the number of teeth on each gear. We know that for each turn of the planet (Tp) the planet will travel around the sun ( Np/Ns ) times (taking the carrier with it in the process) where Np = Planet gear teeth and Ns = Sun gear teeth.

Planetary gearing consists of three elements: a sun gear, a ring gear and a number of planet gears mounted on a carrier. One of these elements is always fixed, one is an input and one is an output. Select gear sizes below and hit CALCULATE to see ratios for all three cases.

A two-stage planetary gear stage is defined using the program. Please start with the tutorial for shaft calculation to see how to introduce geometry and 

2/20 · How to calculate the gear ratio in a planetary gear set where one member is stationary

a) Planetary Type In this type, the internal gear is fixed. The input is the sun gear and the output is carrier D. The transmission ratio is calculated as in 

Epicylic Gears - Ratio Calculation. Purpose of Calculation - To calculate the ratios of various epicylic gear arra

Divide the number of teeth on the driving member by the sum of the sun gear and ring gear teeth on the planetary gear for a system set in 

Let's say your largest acceptable ring gear has 100 teeth, and your largest acceptable planet has 45 teeth, your largest possible reduction (assuming all your gears are of the same module - using different modules in the two stages, one can attain higher gear ratios ) will be 1/[1-(44*100)/(45*99)] = 81 to 1.

This calculator helps generating these possible gear configurations while calculating turn ratios in different scenarios: when ring gear is fixed, 

1/9 · The gear ratio formula for two meshing gears is simple and intuitive, while the gear ratio formula for the planetary mechanism is not. In this tutorial, we

Calulate Gear ratios for the planetary gear of the type 'Split Ring Planetary Gear'. They are mainly used for huge gear ratio reductions for stepper motors