As we all know, the motors have a rated RPM(revolutions per minute) and run at a specific RPM(the actual RPM is usually less than the rated RPM). If you want to keep the motors have a lower RPM, you need to assemble the motor with a Speed Reducer. Then, how to calculate the RPM of the motors assembled with speed reducer? The following is the calculation formula.

Actual RPM = Rated RPM(motor) / Reduction Ratio(speed reducer)
worm speed reducer assembled with motor
worm gearbox assembly with motor

According to the formula, an example is given.

Firstly, you need to know the rated RPM of the motor, for example, 6000 RPM

Secondly, you need to know the reduction ratio of the speed reducer, for example, 10:4, namely, 2.5

Thirdly, the actual RPM is the rated RPM of motor divided by the ratio of speed reducer. In the example, it will be 6000 RPM/2.5 = 2400 RPM