The gear reduction in a right-angle worm drive is dependent on the Planetary Wheel Drive amount of threads or “starts” on the worm and the amount of teeth on the mating worm wheel. If the worm has two begins and the mating worm wheel has 50 teeth, the resulting equipment ratio is 25:1 (50 / 2 = 25).

Calculating the gear ratio in a planetary gear reducer is less intuitive since it is dependent upon the number of teeth of the sun and band gears. The planet gears become idlers and do not affect the apparatus ratio. The planetary gear ratio equals the sum of the number of teeth on the sun and ring gear divided by the amount of teeth on the sun gear. For example, a planetary arranged with a 12-tooth sun gear and 72-tooth ring gear has a equipment ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear models can perform ratios from about 3:1 to about 11:1. If more equipment reduction is needed, additional planetary stages can be used.

If a pinion equipment and its mating gear have the same number of teeth, no decrease occurs and the apparatus ratio is 1:1. The gear is named an idler and its own main function is to improve the path of rotation instead of reduce the speed or boost the torque.

Parallel shaft gearboxes often contain multiple gear sets thereby increasing the gear reduction. The total gear reduction (ratio) is determined by multiplying each individual gear ratio from each equipment set stage. If a gearbox includes 3:1, 4:1 and 5:1 gear pieces, the full total ratio is 60:1 (3 x 4 x 5 = 60). In our example above, the 3,450 rpm electric motor would have its rate reduced to 57.5 rpm by utilizing a 60:1 gearbox. The 10 lb-in electric electric motor torque would be risen to 600 lb-in (before effectiveness losses).