Kilowatt Calculator — AC Single-Phase Power System
Analyze a single-phase AC circuit using kilowatts, RMS voltage, power factor, and RMS current. Enter any three variables and the calculator determines the fourth.
US + metric
Formula shown
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Kilowatt — AC Single Phase
kW
V AC
PF
A AC
Kilowatts1.96kW(1,960 W)
Apparent power (E × I)
2.3 kVA
Real power (E × I × PF)
1,960 W
Formula & method
kW = E · I · PF / 1000
For a single-phase AC circuit, RMS voltage times RMS current gives apparent power in volt-amperes. Multiplying by power factor gives real power in watts; divide by 1000 for kilowatts. Enter power factor as a decimal from 0 to 1. This is electrical input power, so no motor-efficiency term is used.
Assumes a steady single-phase AC supply and RMS voltage, RMS current, and power factor measured at the same operating point. For preliminary and educational use; verify against equipment data and applicable electrical codes.
This calculator analyzes four variables in a single-phase AC circuit: real power in kilowatts, RMS voltage, RMS current, and power factor. Enter any three and it returns the fourth, making it useful for checking measured load, estimating current draw, or finding the power factor implied by a set of readings.
The formula
kW = E · I · PF / 1000. RMS voltage times RMS current gives apparent power in volt-amperes. Multiplying by power factor gives the real power in watts, and dividing by 1000 converts watts to kilowatts. Enter power factor as a decimal between 0 and 1 — for example, 0.85 rather than 85.
Solve in any direction
Kilowatts — the real electrical power drawn by a known voltage, current, and power factor.
Current — the RMS amperage required for a known real-power load.
Voltage — the RMS supply voltage implied by the other readings.
Power factor — real power divided by apparent power; a result above 1.0 identifies inconsistent inputs.
Kilowatts here mean electrical input power
This calculator stops at the real electrical power delivered to the load, so it has no efficiency term. To estimate a motor’s mechanical shaft output, multiply by motor efficiency or use the single-phase horsepower calculator. Do not add an efficiency factor here unless mechanical output is the quantity you actually need.
Single-phase AC assumption
The formula assumes a single-phase AC supply and RMS voltage, RMS current, and power factor taken at the same operating point. A balanced three-phase circuit uses √3 · E · I · PF / 1000, so do not use this single-phase result for a three-phase load.
Worked example
A single-phase load drawing 10 A from a 230 V AC supply at 0.85 power factor has apparent power of 230 × 10 = 2300 VA. Its real power is 2300 × 0.85 = 1955 W, or 1.955 kW.
IEEE 1459 (single-phase AC active and apparent power definitions)SI watt and kilowatt definitions
Verified
Constants and formula two-source checked (PumpCalcs engineering review, 2026-08-25).
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