Electrical Power Calculator

Calculate power, voltage or current using the basic P = V × I relationship

Enter voltage (V) then current (A).

Your result will appear here.

About the Electrical Power Calculator

Electrical power describes the rate at which electrical energy is transferred or used. In a simple circuit it depends on voltage and current, while resistance-based forms can be derived from Ohm’s law.

AC systems can require power factor and phase information, so the simplest volts-times-amps relationship should not be treated as real power for every load.

How to Use the Electrical Power Calculator

  1. Enter the electrical quantities you know, such as voltage and current, or voltage and resistance.
  2. Choose DC, single-phase AC or the supported circuit mode that matches the load.
  3. Enter power factor when real AC power requires it.
  4. Calculate watts and compare the result with equipment ratings before using it for design.

How the Calculation Works

For DC, real power P = V×I. Combining with Ohm’s law also gives P = I²R and P = V²/R.

For single-phase AC, real power is commonly P = V×I×PF. Three-phase systems use the appropriate √3 relationship when line-to-line voltage is entered.

Worked example

Electrical Power Calculator Worked Example

230 V load drawing 5 A at power factor 0.8

Single-phase real power = 230×5×0.8 = 920 W. Apparent power is 230×5 = 1,150 VA, showing why watts and volt-amperes differ when power factor is below 1.

Result guide

Understanding Your Electrical Power Calculator Result

Watts measure real power doing useful work or producing heat. In AC systems, current can be higher than a watts-only estimate suggests when power factor is low.

Before you rely on the answer

Assumptions and Limitations

  • Voltage and current refer to the same operating condition.
  • Phase configuration and power factor are selected correctly.
  • Startup current, harmonics and changing load are outside the simplified steady-state calculation.

Practical tip

Using This Result in Practice

Use equipment nameplate data for circuit planning whenever available. Calculated steady-state power is not a substitute for startup, overload or protection requirements.

Related calculations

Useful Calculations to Continue With

If power and voltage are known and current is the missing quantity, use the Watts to Amps Calculator.

Ohm's Law Calculator — For a purely resistive relationship among volts, amps and ohms, the Ohm’s Law Calculator is the simpler tool.

Common questions

Electrical Power Calculator FAQ

What is the formula for electrical power?

For DC, P=V×I. AC real power may also require power factor and phase information.

What is the difference between watts and VA?

Watts measure real power, while volt-amperes measure apparent power. They are equal only when power factor is 1.

Can I calculate power from resistance?

Yes. With Ohm’s law, P=I²R or P=V²/R for an ideal resistive load.