Motor Efficiency Calculator Online

Motor Efficiency Calculator Online:

Enter the input power and output power in kW or HP. Then click the calculate button, here you see the total efficiency of the motor.

Select Power Unit  
Enter Motor Input Power: kW/HP
Enter Motor Output Power: kW/HP
Result – Efficiency in percentage: %

Motor efficiency calculation:

Efficiency is nothing but a rate of output power with respect to the input power. The net ratio between the output mechanical power to input electrical power is called the efficiency of the motor.

Efficiency (%) = Output Power * 100 / Input Power

Also, motor efficiency will never reach more than or equal to 100%.

Also, look at the formula, the output power is directly proportional to the efficiency of the motor. Hence to get maximum efficiency, always design to run the motor at rated current and RPM.

Generally, motor efficiency is classified into 8 classes such as

  • EFF1
  • EFF2
  • EFF3
  • IE1
  • IE2
  • IE3
  • IE4
  • IE5
Learn More:   VA to Watts Conversion Calculator & Motor Power Chart

Here for simple understanding

IE5 > IE4 > IE3 > IE2 > IE1 > EFF1 > EFF2 > EFF3

IE5 energy class is the highest efficiency motor as well as EFF3 class motors are the lowest energy class motor.


Calculate the efficiency of the motor input power is 55kW and the output power is 45kW.

Apply our formula,

Motor efficiency (%) = 45 * 100 / 55 = 81.8%

The motor has 81.8% efficiency


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