Three-Phase Power Calculator
Find three-phase power from voltage, current and PF.
Default 0.8
Results update as you type.
How it works
Three-phase power is the standard for industrial and commercial electrical systems, and this calculator finds the power it delivers. You enter the line voltage, the line current, and the power factor, and it returns the real power in kilowatts and watts and the apparent power in volt-amperes. The formula for a balanced three-phase system is the square root of three times the line voltage times the line current times the power factor. The square root of three, approximately 1.732, arises from the 120-degree phase difference between the three lines and is what distinguishes three-phase from single-phase power calculations. Real power, in watts or kilowatts, is the actual working power that does useful work, while apparent power, in volt-amperes, is the total power the system must supply; the power factor is the ratio between them, reflecting how much of the current is doing real work versus being reactive. Three-phase power is used for motors, large equipment, and distribution because it delivers power more efficiently and smoothly than single-phase, using less conductor material for the same power. This calculation is essential for sizing generators, cables, and equipment, and for understanding energy use in industrial settings. Line voltage here means the voltage measured between two of the three lines. Use a power factor appropriate to the load; motors are often around 0.8, resistive loads near 1.0. Enter the line voltage, current, and power factor to find the three-phase power.
P = √3 × V_line × I_line × power factor
For a balanced three-phase system, the real power equals the square root of three times the line voltage times the line current times the power factor. The apparent power omits the power factor. The square root of three (about 1.732) accounts for the phase relationship between the three lines.
Source:Electrical engineering
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter line voltage and line current.
- 2
Adjust the options
Adjust power factor if they apply — sensible defaults are already set.
- 3
Read your result
Real power updates instantly as you type — no button to press.
Frequently asked questions
How do you calculate three-phase power?
For a balanced system, multiply the square root of three (about 1.732) by the line voltage, the line current, and the power factor. This gives the real power in watts. Without the power factor, the same product gives the apparent power in volt-amperes. The calculator returns real power in kW and W plus apparent power.
Why is there a square root of three?
The factor of the square root of three, approximately 1.732, comes from the 120-degree phase separation between the three lines in a three-phase system. It relates the line quantities to the phase quantities and is the key difference from single-phase power formulas. It appears whenever you calculate power from line voltage and line current.
What is the difference between real and apparent power?
Real power, in watts or kilowatts, is the power that does actual work, like turning a motor or producing heat. Apparent power, in volt-amperes, is the total power the source must supply, including the reactive component that oscillates without doing net work. The power factor is the ratio of real to apparent power.
What power factor should I use?
It depends on the load. Purely resistive loads like heaters have a power factor near 1.0, while inductive loads like motors and transformers are lower, often around 0.8 or less. Using the actual power factor of your load gives accurate real power. The calculator defaults to 0.8, a common value for mixed industrial loads.
Why is three-phase power used for large loads?
Three-phase power delivers energy more efficiently and smoothly than single-phase, providing constant power to motors and using less conductor material for the same power transmitted. This makes it the standard for industrial machinery, large motors, and power distribution, where its efficiency and ability to run three-phase motors directly are major advantages.