What this converter does
This converter switches between real power (kW, the work done) and apparent power (kVA, what the supply must deliver) using the power factor. Enter your kW and PF to size a generator, transformer or cable — or swap the arrow to go from kVA back to kW. The result updates as you type.
Power factor is the ratio of real to apparent power. A typical motor runs near 0.8; a resistive heater is 1.0. Lower PF means more kVA for the same kW. For the mechanical side of a motor rating, see the kW to HP converter.
The units it covers
These are the three faces of AC power plus the ratio that links them — kVA is the vector sum of kW and kVAR.
View all units & their values
| Unit | Symbol | Value | Mainly used |
|---|---|---|---|
| Real power | kW | P | Useful work; the energy you are billed for |
| Apparent power | kVA | S | Sizing generators, transformers, cables |
| Reactive power | kVAR | Q | Magnetising motors and transformers |
| Power factor | PF | P÷S | Ratio 0–1; how much apparent power does work |
The formula
Apparent power is real power divided by the power factor:
kVA = kW ÷ PF (and kW = kVA × PF)Where:
- kW = real power — the useful work delivered
- kVA = apparent power — what the supply must carry
- PF = power factor, between 0 and 1
Worked example
A 20 kW motor runs at a power factor of 0.8. Find its apparent power.
kVA = kW ÷ PF20 ÷ 0.8 = 25 kVAThe supply must carry 25 kVA to deliver 20 kW of real work at 0.8 PF.
The units in this example
The power that does useful work — turning a motor, producing heat or light. It is what an energy meter bills and equals kVA × power factor.
- kW = kVA × PF
- 1 kW = 1.25 kVA at 0.8 PF
- 1 kW = 1 kVA at unity PF
- 1 kW = 1,000 watts
The total power the supply must deliver — the vector sum of real and reactive power. Generators, transformers and cables are sized in kVA.
- kVA = kW ÷ PF
- 1 kVA = 0.8 kW at 0.8 PF
- 1 kVA = 1 kW at unity PF
- 1 MVA = 1,000 kVA