About the kVA to Watts Calculator
Generators, UPS units and transformers are rated in kVA, but the appliances you plug into them are rated in watts. This calculator converts kVA into the real power in watts by multiplying by 1,000 and by the power factor. It also shows the kilowatts and the reactive power in kVAR, the part of the current that flows back and forth without doing work. Type the kVA and the power factor and the answer appears instantly, worked out on your own device.
Updated October 2026
How to use the kVA to Watts Calculator
- 1Enter the apparent power in kVA from the rating plate or the datasheet.
- 2Enter the power factor. Use 0.8 if the label doesn't give one; it is the standard figure for generators.
- 3Read the real power in watts.
- 4Check the kW and kVAR rows underneath.
- 5Copy the result if you need it elsewhere.
Reading a generator or UPS label
Most labels show both figures, for example 6.25 kVA / 5 kW. The kVA figure is the limit of the alternator or the electronics; the kW figure is what you can actually run at the rated power factor. If only kVA is printed, this calculator gives you the usable watts, which you can compare with the total wattage of the appliances you plan to connect.
Choosing the power factor
Use 1 for resistive loads such as heaters, kettles and incandescent lamps. Use about 0.9 to 0.95 for modern computers and LED drivers with power factor correction. Use 0.8 for a general mix or when you have no information, and 0.7 or lower for older motors running lightly loaded.
- Resistive heaters: 1.0
- Modern electronics: 0.9–0.95
- General mix and generators: 0.8
- Lightly loaded motors: 0.7 or less
Worked examples
A 3 kVA UPS with a power factor of 0.9 can supply 2,700 W. A 500 kVA transformer feeding a factory at a power factor of 0.85 delivers 425 kW of real power and carries about 263 kVAR of reactive power. A small 2 kVA inverter rated at 0.8 should not be loaded beyond 1,600 W.
On phone and computer
The calculator works the same on any screen. On a phone, type the two numbers and the watts appear underneath; on a computer the answer sits beside the inputs. The sums run in your browser and nothing is stored. VA and watts differ by the power factor, so keep it in mind. Use the Power Factor Calculator to find that figure, the kVA to kW Calculator for large loads, and the kVA to Amps Calculator to check the current.
Features
- kVA to W and kW
- Reactive power in kVAR
- Works for single-phase and three-phase
- Explains the 0.8 power factor
- Copy the result with one tap
- Private: nothing is sent anywhere
Frequently asked questions
How many watts is 1 kVA?
1 kVA is 1,000 VA. At a power factor of 0.8 it gives 800 W; at a power factor of 1 it gives 1,000 W.
What is the formula for kVA to watts?
Watts = kVA × 1,000 × power factor. For a 5 kVA generator at 0.8 that is 5 × 1,000 × 0.8 = 4,000 W.
Why do generators use a power factor of 0.8?
Manufacturers rate standby generators at 0.8 because typical mixed loads, with motors and electronics, have a power factor near that. So a 10 kVA generator is usually sold as 8 kW.
Does single-phase or three-phase change the answer?
No. kVA already includes the √3 for three-phase, so watts = kVA × 1,000 × power factor in both cases.
What is kVAR?
Kilovolt-amps reactive, the power that moves back and forth in motors and transformers without being used up. kVA² = kW² + kVAR², so a lower power factor means more kVAR for the same kVA.
How do I convert watts back to kVA?
Divide by 1,000 and by the power factor: kVA = W ÷ (1,000 × PF). Our Watts to kVA calculator does that for you.