Single-Phase Power Calculator
Calculate real power in watts for a single-phase AC circuit from voltage, current, and power factor.
Estimates for planning only — verify against local wiring codes and a qualified electrician before installation.
How it works
- 1Enter the supply voltage (e.g. 230 V or 120 V).
- 2Enter the current in amperes and set the power factor (use 1 for resistive loads).
- 3The calculator applies P = V × I × pf and shows watts, kW, apparent power, and horsepower.
Use cases
- Sizing breakers and cable for domestic or light industrial loads.
- Estimating energy use by converting watts to kilowatt-hours.
- Comparing real power to apparent power to gauge power-factor effects.
Frequently asked questions
What is the single-phase power formula?
Real power P = V × I × pf. A 230 V, 10 A resistive load (pf = 1) gives P = 230 × 10 = 2300 W.
What is the difference between W and VA?
Apparent power S = V × I (VA) ignores phase; real power P = S × pf is the useful work. For resistive loads pf = 1 so they are equal.
How do I find power factor from W and VA?
Power factor = P ÷ S. A motor drawing 1800 W with 2000 VA has pf = 0.9.
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