Gear Ratio Calculator

A single stage is one gear pair. Two stages chain a second pair onto the output of the first, multiplying the two ratios — the way to get large reductions with small gears.

Tooth count of the input (driving) gear — the one connected to the motor or crank.

Tooth count of the output (driven) gear. More teeth than the driver means a slower but stronger output: 20 → 60 teeth is a 3:1 reduction.

Tooth count of the second stage’s driving gear, mounted on the same shaft as the first stage’s driven gear.

Tooth count of the final driven gear; the total ratio is the product of both stage ratios.

How fast the input shaft spins, in revolutions per minute; the output speed is this divided by the total ratio.

The turning force on the input shaft, in newton-metres. The ideal output torque is this times the ratio; real gears lose a few percent to friction.