About the kVA to kW Calculator
This calculator moves between kVA, kW and amps. kVA is apparent power, the figure printed on generators, transformers and UPS units. kW is the real power that does the work, and the two are linked by the power factor. Choose a conversion, type the value and the power factor, and the result appears together with kVA, kW and reactive power (kVAR). For the amps modes you also enter the voltage and pick single-phase or three-phase. The page uses the power factor you type. It does not derate a generator for altitude or heat, and it does not work out starting current for motors, so keep a safety margin when you choose equipment.
Updated October 2026
How to use the kVA to kW Calculator
- 1Choose the conversion: kVA to kW, kW to kVA, kVA to amps or amps to kVA.
- 2Type the value you know.
- 3Set the power factor, or tap 0.7, 0.8, 0.9 or 1.0.
- 4For amps, type the voltage and choose single-phase or three-phase.
- 5Read the answer and the table with kVA, kW, kVAR and current.
kVA, kW and power factor
Real power in kilowatts equals apparent power in kilovolt-amperes multiplied by the power factor. If the power factor is 0.9, a 50 kVA supply can deliver 45 kW. Improving the factor with correction capacitors lets the same equipment carry more real load.
Reactive power, in kVAR, is what remains: its square is the square of kVA minus the square of kW. The page shows it in the results table whenever those two values are known.
Converting for generators and UPS
Generator sets and UPS units are usually labelled in kVA, while equipment lists give watts or kilowatts. Convert your total load to kVA by dividing by the power factor, then compare it with the label. Some UPS units are rated directly in kW at a power factor of 0.9 or 1, so read the data sheet.
Motors, pumps and compressors need extra capacity to start. Add up the loads that can start together and leave headroom instead of sizing to the running total.
kVA to amps, single- and three-phase
- Single-phase: amps = kVA × 1,000 ÷ volts.
- Three-phase: amps = kVA × 1,000 ÷ (1.732 × line voltage).
- Use the line-to-line voltage for three-phase, for example 400 V or 415 V.
- The amps modes assume a balanced load across the phases.
- For a watts-based view of the same circuit, use the Watts, Amps and Volts Calculator.
Sizing with a safety margin
Nameplate figures are maximums. A supply that runs at its limit all day heats up and wears faster, so most designers keep continuous load under about 80 percent of the rating. Altitude, high temperature and dusty air lower a generator's output, and this page does not adjust for them.
Use the answers here as a starting point for a conversation with a supplier or an electrician, who will look at the real loads, the starting currents and the local rules. For amps and volts use the Watts, Amps and Volts Calculator, and for unit swaps the Unit Converter. For other power sums use the Online Calculator, and the Unit Converter handles unit swaps.
Features
- kVA to kW and kW to kVA
- kVA to amps and amps to kVA
- Single-phase and three-phase
- Power factor quick buttons
- Reactive power (kVAR) shown when it can be worked out
- Typical power factor list for common equipment
- Runs in your browser
Frequently asked questions
What is the difference between kVA and kW?
kVA is the total electrical load a supply must carry, while kW is the part of it that becomes useful work such as motion, light or heat. They are equal only when the power factor is 1. Otherwise kW is smaller than kVA.
How do I convert kVA to kW?
Multiply the kVA by the power factor. A 10 kVA generator with a power factor of 0.8 gives 8 kW. To go the other way, divide the kW by the power factor, so 8 kW at 0.8 needs 10 kVA.
What power factor should I use for a generator?
Most generators are rated at 0.8, which is why a 100 kVA set is sold as 80 kW. Your actual load may have a different factor, so check the nameplate of the equipment and use that figure when you know it.
How do I convert kVA to amps for 3-phase?
Multiply the kVA by 1,000 and divide by 1.732 times the line voltage. For 10 kVA at 400 V that is about 14.4 A. Choose the kVA to amps mode, enter 400 V and select three-phase.
Why is kVA bigger than kW?
Part of the current in an AC circuit swings back and forth without doing work, mostly in motors and transformers. The supply still has to carry that current, so kVA counts it and kW does not. The difference is the reactive power in kVAR.
What size generator do I need for 20 kW?
At a power factor of 0.8, 20 kW is 25 kVA. Add a margin for motors that draw a large current when they start, often 20 to 30 percent or more, and choose the next size up. A supplier can confirm the rating for your exact loads.