Equating hertz and revolutions per minute

A rotational speed of 50 Hz corresponds to 50 revolutions per minute.

50 Hz is 3000 rpm. The factor between the two figures is 60, because a minute has 60 seconds.

Hertz counts events per second, rpm per minute. Both describe the same kind of event — periodic repetition — with a different time unit. Depending on industry and manufacturer, datasheets state one or the other.

To convert hertz to rpm multiply by 60; for the other direction divide by 60. Mains frequency of 50 Hz therefore equals 3000 rpm, which is directly relevant to the speed of synchronous motors and to mains-driven clocks.