Enter the hertz (hz) and the number of poles into the Calculator. The calculator will evaluate the RPM from Hz. 

RPM from Hz Formula

RPM = HZ * 60 * 2 / P


  • RPM is the RPM from Hz (rotations per minute)
  • HZ is the hertz (hz)
  • #P is the number of poles

To calculate RPM from Hz, multiply the hertz by 120, then divide by the number of poles.

How to Calculate RPM from Hz?

The following steps outline how to calculate the RPM from Hz.

  1. First, determine the hertz (hz). 
  2. Next, determine the number of poles. 
  3. Next, gather the formula from above = RPM = HZ * 60 * 2 / #P.
  4. Finally, calculate the RPM from Hz.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

hertz (hz) = 150

number of poles = 4

Frequently Asked Questions

What is Hertz (Hz) and how does it relate to RPM?

Hertz (Hz) is a unit of frequency that measures the number of cycles per second. In the context of RPM (rotations per minute), it relates to how many times a mechanical component completes a full rotation within one minute. The relationship between Hz and RPM is directly affected by the number of poles in the motor, as outlined in the calculation formula.

Why do we need to know the number of poles to calculate RPM from Hz?

The number of poles in a motor or generator is crucial for calculating RPM from Hz because it directly influences the speed at which the motor operates. The formula incorporates the number of poles to accurately determine the rotations per minute, as each pole pair’s presence affects the electrical cycle completion rate.

Can this formula be used for any type of motor?

While the formula provided is a standard method for calculating RPM from Hz, it’s important to note that it applies primarily to synchronous motors, where the rotational speed is directly related to the frequency of the electrical supply and the number of poles. For other types of motors, such as induction motors, the relationship might slightly vary due to slip.

How can inaccuracies in calculating RPM from Hz be minimized?

To minimize inaccuracies in calculating RPM from Hz, ensure that the input values for Hz and the number of poles are as accurate as possible. Additionally, using a calculator specifically designed for these calculations can help reduce errors. Understanding the type of motor and its characteristics can also aid in making more precise calculations.