Frequency is a way to describe oscillatory motion, such as that by a particle or wave. It describes the time it takes for a motion to repeat itself. It is measured in hertz, which is one oscillation per second. Revolutions per minute denotes circular motion, or the rotations completed by an object around an axis. For motors, the term tells how quickly they can rotate when not under a load. The frequency of a motor can be converted to rpm and vice versa.
Determine what your starting frequency is. For example, suppose that a motor rotates at 65 hertz, which means that it completes 65 revolutions per second.
Calculate your conversion factor to convert hertz to rpm. One hertz is equal to 60 rpm, since there are 60 seconds in a minute.
Multiply your frequency by 60. In the example, you would multiply 65 hertz by 60 to get 3,900 rpm.
To convert from rpm to hertz, divide any given rpm by 60.