Enter the measured three-phase power and the input power at full-rated load into the calculator to determine the motor load percentage.

Motor Load Formula

The following formula is used to calculate the motor load of an electric motor.

L = Pm / Pi *100
  • Where L is the motor load (%)
  • Pm is the measured three-phase power (kW)
  • Pi is the Input Power at full-rated load (kW)

To calculate the motor load, divide the three-phase power by the input power, then multiply by 100.

Motor Load Definition

A motor load is defined as the ratio of the measured power to the full rated power that a motor is running at. This ratio can be expressed in percentage by multiplying it by 100 as seen in the formula above.

Motor Load Example Problem

How to calculate motor load?

  1. First, determine the measured three-phase power.

    For this example, the measured power is found to be 500 kW using the current and amps.

  2. Next, determine the full-rated load.

    This is most often published data by the manufacturer of the motor. For this problem, the rated load is 1000 kW.

  3. Finally, calculate the motor load.

    The motor load can be calculated using the formula above. ML = Pm/PI *100 = 500/1000 *100 = 50%.


What is motor load?

A motor load is a percentage of the full rated power that a motor is currently running at. The full rated power is the maximum power the motor can run at.

Can the motor load be greater than 100%?

Motors can and do run at greater than 100%, or more than their maximum rated power. In most cases, this will cause damage to the motor, but it does not mean it cannot run at higher rates temporarily.

What happens when motor load increases?

An increase in motor load will cause a motor to run at a higher power, and likely a higher heat as more energy is going into the motor.

motor load calculator