Gear Ratio Calculator

This calculator turns tooth counts into a gear ratio. The first mode takes up to three meshing pairs in series and returns each stage ratio, the overall ratio as a decimal and as a reduced fraction, the output speed and torque, and which way the output shaft turns. The second takes the teeth on a differential ring gear and its pinion and returns the final drive ratio, whether the pair is a hunting set, and the tooth counts that come closest to a ratio you are aiming for. Efficiency per mesh is optional and only affects torque, not speed. Ratios go in as teeth, so nothing here depends on gear size or pitch.