Reactive Power Calculator

Enter the true power and the apparent power into the calculator to determine the reactive power.

Reactive Power Formula

The following formula is used to calculate an reactive power value.

RP = SQRT ( AP^2 – TP^2)

  • Where RP is the reactive power
  • AP is the apparent power
  • TP is the true power.

Reactive Power Definition

A reactive power is the amount or proportion of power that is out-of-phase with the other transmitting powers, known as the true power and apparent power.

Is reactive power good or bad?

In general a reactive power will be good for an electric system. The reactive power provided to or by the system is used to regulate the voltage of a system. For example, if the voltage is not high enough in a system then the active power may not be supplied. A reactive power is then introduced to increase the voltage and allow the active power to transfer and do work.

How does reactive power affect voltage?

In general, an increase in reactive power is accompanied by an increase in voltage, and a decrease in reactive power is accompanied by a decrease in voltage. Depending on the system, these may not hold true, but for the majority of currents this does apply.

Does DC have reactive power?

By definition a reactive power is a byproduct of an alternating current where the voltage and current are out of phase. As a result a DC current does not have or required a reactive power component.

Can a reactive power be 0?

Reactive power can be zero when the phase angle between the voltage and current is the same. In these cases, the system is said to have a power factor unity. In these types of electrical systems, only real power is consumed by the circuit.

Reactive Power Example

How to calculate a reactive power?

  1. First, determine the apparent power.

    Calculate the apparent power.

  2. Next, determine the true power.

    Calculate the true power.

  3. Finally, calculate the reactive power.

    Calculate the reactive power using the equation above.


What is reactive power?

A reactive power is the total power, known as volts times amperes, that are out-of-phase with each other. It’s the portion of electricity that sustains the electric and magnetic fields needed for alternating current equipment.

reactive power calculator
reactive power formula