Gear Ratio Calculator
Ratio, output speed and torque multiplication for a gear pair or train.
How it works
Gear ratio is driven teeth divided by driver teeth. A 36-tooth gear driven by a 12-tooth pinion is 3:1 — the output turns a third as fast and, minus losses, with three times the torque.
Power is what stays constant. Speed and torque trade against each other, which is the entire purpose of a gearbox. Stages multiply: 3:1 followed by 4:1 gives 12:1.
Each meshing pair reverses direction, so an even number of stages restores the original sense of rotation and an odd number inverts it.