# Electrical Power Calculator

Created by Luciano Mino
Last updated: Aug 06, 2022

The electrical power calculator quickly computes the amount of power an electrical device needs.

With our tool, you will learn:

• How to calculate electrical power;
• The electrical power equation;
• The definition of power factor; and

## Electrical power definition

Electrical power is the transfer rate of electrical energy per time unit.

We denote the electrical power by $P$, and its unit is the watt (W) or joules per second (J/s).

The power needed by home appliances generally ranges from 10 W (an LED light bulb) to over 3 kW (hair dryers or electric heaters).

Let's now see how to calculate electrical power.

## How to calculate electrical power using the electrical power equation

To calculate a device's electrical power $P$ in a DC circuit, we need two things:

• The current $I$, in amperes (A).
• The voltage $V$, in volts (V).

Then, all we need to do is replace these parameters in the electrical power equation:

$P = I \times V$

However, if we're calculating the power in an AC circuit, we should add the device's power factor $pf$ in the equation:

$P = I \times V \times pf$

If you don't know what the power factor is, read the following section!

💡 This electrical power calculator works for both DC and AC. To use this tool as an AC power calculator, simply replace the current and voltage values with their root mean square values!

## Power factor

The power factor is the ratio between real power (power used to perform work) and apparent power (combination of real and reactive power).

In other words, the power factor of a device indicates how effectively it utilizes the power supplied to the circuit. Therefore, a higher power factor is desirable since it means a more efficient device.

If you want a more in-depth explanation, check our power factor calculator!

Luciano Mino
Voltage
V
Current
A
Power factor
Power
W
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