Science & Engineering
Gear ratio.
Use tooth counts to estimate reduction, output speed, and output torque for a single external gear pair.
Inputs
Result
Fill the form and press Calculate.
Gear ratio formula
For one pair of meshing external gears, ratio = driven teeth ÷ driver teeth. Output speed is input speed divided by the ratio. Ideal output torque is input torque multiplied by the ratio; this page applies the efficiency you enter to estimate transmitted torque.
Reference: OpenStax, torque and rotational-motion key equations. The result assumes matching pitch, rigid gears, and one stage.
Mechanical note
This does not check tooth strength, interference, backlash, shaft loads, bearing losses, or gearbox ratings.