3-Phase Power Calculator

For line-to-line voltage, real power P = sqrt(3) x V x I x PF. For line-to-neutral (phase) voltage, it's P = 3 x V x I x PF. Both formulas describe the same underlying physics; which one applies depends on whether the voltage you measured or were given is line-to-line or line-to-neutral, which is why this calculator lets you choose.

Line-to-line voltage is measured between any two of the three phase conductors, while line-to-neutral (phase) voltage is measured between one phase conductor and the neutral wire. In a standard wye-connected system, line-to-line voltage is always sqrt(3) (about 1.732) times the line-to-neutral voltage, for example a system with 230V line-to-neutral has roughly 400V line-to-line.

Power factor is a number from 0 to 1 (or occasionally shown as leading/lagging) that describes how effectively the current is actually doing useful work, versus energy that flows back and forth without ever being consumed, caused by motors, transformers, and other inductive loads. A power factor of 1.0 means all the apparent power is real, usable power; anything less means part of the current is "wasted" moving reactive power around, which still costs money on many utility bills and stresses wiring and equipment.

Real power (P, measured in watts) is the power actually converted into useful work, like heat, light, or motion. Apparent power (S, in volt-amps) is the total power the system delivers, real and reactive combined, and is what your wiring and equipment actually have to be rated for. Reactive power (Q, in VAR) is the portion that oscillates back and forth without being consumed, typically from magnetic fields in motors and transformers. They relate through the power triangle: P squared plus Q squared equals S squared.

This comes up when you're sizing wiring, breakers, or other equipment for a known load: a motor or piece of equipment is rated in kW, and you need to know how many amps it will actually draw at your system's voltage and expected power factor, in order to choose a correctly-rated cable or breaker.

The formulas are the same standard formulas used throughout electrical engineering, but treat this as a planning and estimation tool rather than a substitute for a qualified electrician's judgment, especially for anything involving code compliance, safety margins, or equipment sizing where real-world factors like temperature derating, cable length voltage drop, and harmonic distortion also come into play.

It depends entirely on your local electrical system, common values include 208V and 480V line-to-line in North America, and 400V line-to-line (230V line-to-neutral) in much of Europe and beyond, which is why quick preset buttons for these common voltages are included. Check the equipment's nameplate or your electrical system's documentation for the exact figure rather than assuming.