Gear ratio calculator and motor simulator
Calculate Technic-style gear ratios and compare estimated motor RPM, torque and wheel speed. Try animated gear trains, then test a free build.
Compare Technic-style gear trains before you build. Choose a motor, driver and driven gears, then see estimated output speed, torque and wheel speed in the Motor + Gear Lab.
How to calculate a gear ratio
For a single pair, divide the driven gear’s tooth count by the driver gear’s tooth count. This calculator uses input turns per output turn: an 8-tooth driver turning a 24-tooth driven gear has a 3:1 reduction. The output turns once for every three input turns. Reverse the pair for three output turns per input turn.
Calculate output RPM and compare torque
Output RPM equals input RPM divided by the reduction ratio. With a 3:1 reduction, an input of 300 RPM gives an ideal output of 100 RPM. Reduction increases ideal output torque while reducing speed. Multiply the ratios for stages connected in series. An idler between two gears changes direction, but does not change their final speed ratio.
Turn a prediction into a fair test
Try the Race, Climb, Crane and Spin presets, then change one setting at a time. Compare the same motor and wheels with a different gear pair. The lab estimates performance; actual speed and lifting depend on motor load, battery condition, friction and grip. Check your parts and test the physical model rather than treating a prediction as a measured result.