Three-Phase Power Calculator
Calculate real and apparent power in balanced three-phase AC systems from line values.
Estimates for planning only — verify against local electrical codes and a qualified professional.
How it works
- 1Enter the line-to-line voltage VL (e.g. 400 V).
- 2Enter the line current IL drawn by the load.
- 3Enter the power factor (0–1). Real power P = √3 × VL × IL × pf is computed instantly.
Use cases
- Sizing breakers and cables for three-phase motors and equipment.
- Verifying generator or UPS capacity against three-phase loads.
- Converting between watts, kW, VA, and horsepower for datasheets.
Frequently asked questions
What is the three-phase real power formula?
P = √3 × VL × IL × pf using line values. For 400 V, 10 A, pf 0.8: P = 1.732 × 400 × 10 × 0.8 ≈ 5543 W (≈ 5.54 kW).
How does apparent power differ from real power?
Apparent power S = √3 × VL × IL (VA) is the total supplied; real power P = S × pf is the useful portion. The difference is reactive power.
Why use line values?
Line voltage and current are what you measure at the terminals and read on nameplates. The √3 factor accounts for the 120° phase displacement.
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