Electrical Power Calculator (Single and Three Phase)
Work out watts, kVA and kvar from volts, amps and power factor.
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Electrical Power Calculator (Single and Three Phase) by TheCalcTools
How the Electrical Power Calculator (Single and Three Phase) works
Choose single or three-phase, then enter the voltage, current and power factor.
Apparent power is volts times amps, multiplied by √3 for three-phase line values.
Real power is apparent power times the power factor.
The formula
Worked example
Using the default values shown in the calculator:
| Supply | Single phase |
|---|---|
| Voltage (V) | 230 |
| Current (A) | 10 |
| Power factor | 0.9 |
- Apparent power = 230 × 10 = 2,300 VA.
- Real power = 2,300 × 0.9 = 2,070 W.
- Reactive power = 1,002.5 var.
Result:
| Apparent power (VA) | 2,300.0 |
|---|---|
| Real power (W) | 2,070.0 |
| Reactive power (var) | 1,002.5 |
| Real power (kW) | 2.070 |
Frequently asked questions
What is power factor?
The ratio of real power to apparent power. Inductive loads such as motors lower it, which means more current is needed for the same useful power.
What is the difference between kW and kVA?
kW is real power doing work. kVA is apparent power, the product of volts and amps. They are equal only when the power factor is 1.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.