What is the power triangle?

The power triangle is a right-triangle representation of AC power where real power (P, watts) forms the base, reactive power (Q, VAR) forms the height, and apparent power (S, VA) is the hypotenuse. The relationship is S² = P² + Q², derived from the Pythagorean theorem.

What is power factor?

Power factor (PF) is the ratio of real power to apparent power: PF = P / S = cos φ. It ranges from 0 to 1 (or 0% to 100%). A PF of 1 means all power is doing useful work; lower values indicate reactive power is present.

What is reactive power and why does it matter?

Reactive power (VAR) is energy stored and released each cycle by capacitors and inductors. It does no net work but increases current in conductors, causing extra losses and voltage drop. Utilities may charge penalties for poor power factor.

Can I enter apparent power and power factor directly?

Yes — enter apparent power (VA) plus real power (W). The tool derives reactive power and phase angle. Alternatively, supply real and reactive power directly. All three two-variable combinations are supported.

What units does the calculator use?

Real power in watts (W), reactive power in volt-amperes reactive (VAR), and apparent power in volt-amperes (VA). For large systems, enter values in kilowatts, kVAR, and kVA and interpret results in the same prefix.

Power Triangle Calculator

Name: Power Triangle Calculator
Availability: InStock
Author: Nham Vu

Enter any two of real power (W), reactive power (VAR), or apparent power (VA) to compute the remaining values and power factor.

Known Quantities

Enter any two values; leave the third blank.

Real Power — P (W)

Reactive Power — Q (VAR)

Apparent Power — S (VA)

Summary

Enter any two of real power (W), reactive power (VAR), or apparent power (VA) to compute the remaining values and power factor.

How it works

Select which two quantities you know from the three options: real power (W), reactive power (VAR), or apparent power (VA).
Enter the numeric values for your two known quantities.
Click Calculate to apply the power triangle formulas (S² = P² + Q²).
Results show the third power quantity, power factor (cos φ), and phase angle in degrees.
Use the Reset button to start a new calculation.

Use cases

Size capacitor banks to correct power factor toward unity.
Verify motor nameplate VA ratings against measured watt and VAR readings.
Estimate reactive power compensation needed for industrial loads.
Cross-check energy meter readings against apparent power billing.
Teach AC power theory with an instant visual power triangle diagram.
Calculate phase angle between voltage and current in AC circuits.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu