The gear decrease in a right-angle worm drive is dependent on the amount of threads or “starts” on the worm and the number of teeth on the Planetary Wheel Drive mating worm wheel. If the worm has two starts and the mating worm wheel offers 50 tooth, the resulting equipment ratio is 25:1 (50 / 2 = 25).
Calculating the apparatus ratio in a planetary gear reducer is much less intuitive since it is dependent on the number of teeth of sunlight and ring 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 sunlight and ring equipment divided by the amount of teeth on sunlight gear. For instance, a planetary established with a 12-tooth sun gear and 72-tooth ring gear has a equipment ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear sets can achieve ratios from about 3:1 to about 11:1. If more gear reduction is needed, additional planetary stages can be used.
If a pinion equipment and its mating gear have the same number of teeth, no reduction occurs and the apparatus ratio is 1:1. The apparatus is named 
an idler and its own major function is to improve the path of rotation rather than decrease the speed or raise the torque.
Parallel shaft gearboxes many times contain multiple gear sets thereby increasing the apparatus reduction. The total gear reduction (ratio) depends upon multiplying each individual gear ratio from each equipment arranged stage. If a gearbox includes 3:1, 4:1 and 5:1 gear units, the full total ratio is 60:1 (3 x 4 x 5 = 60). Inside our example above, the 3,450 rpm electric electric motor would have its quickness reduced to 57.5 rpm by utilizing a 60:1 gearbox. The 10 lb-in electric engine torque would be risen to 600 lb-in (before effectiveness losses).