Work out gear ratio instantly with clear inputs, formula shown and shareable results.
Gear ratio is driven teeth over driver teeth. A 20-tooth gear driving a 60-tooth gear is a 3:1 reduction, so output speed is a third of input while torque triples - power is conserved apart from mesh losses. Ratios below one are overdrives, trading torque for speed.
Gear ratio
ratio = driven teeth / driver teeth
Speed and torque
output rpm = input rpm / ratio; output torque = input torque x ratio
Because power is torque times angular speed and gears do not create power. Cutting speed threefold must triple torque to keep the product the same.
Not for the ratio - only tooth counts do. Pitch has to match between meshing gears for them to run at all, though.