What is the formula for three-phase apparent power?

Apparent power (S) = √3 × V_L × I_L, where V_L is the line-to-line voltage and I_L is the line current. The result in VA is divided by 1000 to give kVA.

How is active (real) power calculated?

Active power (P) = S × cos(φ), where cos(φ) is the power factor. It represents the actual energy consumed by the load, measured in kW.

What is reactive power (kVAR)?

Reactive power (Q) = S × sin(φ). It represents power stored and released by inductive or capacitive elements and does not perform useful work, but must be supplied by the source.

What is the difference between lagging and leading power factor?

A lagging power factor means the current lags the voltage — typical of inductive loads like motors. A leading power factor means current leads voltage — typical of capacitive loads or over-excited synchronous machines.

Does this work for unbalanced three-phase systems?

No. This calculator assumes a balanced (symmetrical) three-phase system where all three phases carry equal current. For unbalanced systems, each phase must be calculated individually.

What voltage should I enter — line or phase?

Enter the line-to-line (line) voltage. For a star (Y) system this is √3 × phase voltage. For a delta system it equals the phase voltage. Standard values: 208 V, 415 V, 480 V, 690 V.

Three Phase Power Calculator

Name: Three Phase Power Calculator
Availability: InStock
Author: Nham Vu

Enter line voltage, current, and power factor to instantly calculate apparent, active, and reactive three-phase power.

System Parameters

Line-to-Line Voltage (V)

Common values: 208 V, 415 V, 480 V, 690 V

Line Current (A)

Power Factor (0 – 1)

Power Factor Type

Lagging (inductive) Leading (capacitive)

Efficiency % (optional, for output kW)

Leave blank to skip shaft/output power estimate

Power Results

Enter values on the left and click Calculate.

Power Triangle Reference

Apparent (kVA)

√(P² + Q²)

Active (kW)

S × cos φ

Reactive (kVAR)

S × sin φ

Summary

Enter line voltage, current, and power factor to instantly calculate apparent, active, and reactive three-phase power.

How it works

Enter the line-to-line voltage in volts (e.g. 415 V for a standard industrial supply).
Enter the line current in amperes drawn by the load.
Enter the power factor as a decimal between 0 and 1 (e.g. 0.85).
Select lagging or leading to indicate whether the load is inductive or capacitive.
The calculator instantly computes apparent power (kVA), active power (kW), and reactive power (kVAR).
Results update in real time as you change any input.

Use cases

Size generators, transformers, and switchgear for industrial installations.
Verify that a motor drive or UPS system meets load requirements.
Calculate power factor correction capacitor sizing.
Estimate electricity costs based on active power consumption.
Cross-check nameplate data on three-phase motors and panels.
Educational use — visualize the power triangle relationship.
Quick field calculations during commissioning or maintenance.
Convert between apparent, active, and reactive power quantities.

Frequently Asked Questions

Last updated: 2026-06-13 · Reviewed by Nham Vu