Calculation reviewed: 14 October 2026 · Engineering Desk Tools · How we check calculations
This kVA to kW calculator converts apparent power (kVA) to real power (kW) and back again, using the power factor. It also shows the reactive power (kVAR), so you can see the full power triangle. Use it for generators, transformers, UPS units and any load that has a kVA rating on the nameplate.
kVA to kW formula
kW = kVA × PF
PF is the power factor, written as a decimal (0.8, not 80 %). Example: a 100 kVA generator at 0.8 power factor gives 100 × 0.8 = 80 kW. A 500 kVA transformer feeding a load at 0.9 power factor can deliver 450 kW.
kW to kVA formula
kVA = kW ÷ PF
Example: a 75 kW load at 0.85 power factor needs 75 ÷ 0.85 = 88.2 kVA of supply capacity. Use this when you know the real load in kW and need to size a generator, transformer or UPS, which are all rated in kVA.
kVA vs kW: what is the difference?
kVA is always equal to or larger than kW. They are equal only when the power factor is 1, which is true for purely resistive loads such as heaters. Motors, transformers and fluorescent lighting draw reactive current, so for them kW is lower than kVA.
kVA to kW conversion chart
kW to kVA conversion chart
Generator kVA to kW (0.8 power factor)
Diesel generator sets are normally rated in kVA at a power factor of 0.8 lagging, which is the rating basis used in ISO 8528-1. So the kW rating of a generator is its kVA rating × 0.8. A 500 kVA generator is a 400 kW generator. The table also shows the full-load current, which you can check with the kVA to amps calculator.
Single-phase and three-phase
The kVA to kW formula is the same for single-phase and three-phase supplies, because both kVA and kW already describe total power. The number of phases only matters when you go to current: use the kW to amps calculator or the kVA to amps calculator for that step.
How to use the kVA to kW calculator
Choose the direction (kVA to kW, or kW to kVA), enter the power value and enter the power factor as a decimal between 0 and 1. Select Calculate. The result shows real power, apparent power and reactive power together. If you do not know the power factor, take it from the equipment nameplate or a power analyser reading; use 0.8 for a generator rating.
Inputs and measurement basis
- Power (kVA or kW): the rating or measured value. Use the same operating condition for power and power factor.
- Power factor: displacement power factor from the nameplate, a data sheet or a measurement. Lagging and leading loads both use the same number here.
Method and interpretation
The calculator multiplies or divides by the power factor, then finds reactive power from the power triangle: kVAR = √(kVA² − kW²). Harmonic currents are not included; on loads with drives or rectifiers, the true power factor from a power analyser can be lower than the displacement power factor.
Worked example
A 250 kVA transformer supplies a plant with an average power factor of 0.85. Real power capacity = 250 × 0.85 = 212.5 kW. Reactive power = √(250² − 212.5²) = 131.7 kVAR. If power factor correction raises the power factor to 0.95, the same transformer can carry 237.5 kW, an extra 25 kW, without exceeding its kVA rating. See the power factor correction calculator for the capacitor kVAR.
Common mistakes
- Entering power factor as a percentage (85) instead of a decimal (0.85).
- Treating kVA and kW as the same thing when sizing a generator or UPS. A 100 kW load at 0.8 PF needs 125 kVA.
- Using motor efficiency in place of power factor. Efficiency links shaft kW to input kW; power factor links input kW to kVA.
- Comparing a standby generator rating with a continuous load.
Frequently asked questions
How do you convert kVA to kW?
Multiply kVA by the power factor: kW = kVA × PF. For example, 100 kVA at 0.8 power factor is 80 kW.
How do you convert kW to kVA?
Divide kW by the power factor: kVA = kW ÷ PF. For example, 80 kW at 0.8 power factor is 100 kVA, and 75 kW at 0.85 is 88.2 kVA.
How many kW is 1 kVA?
1 kVA is 0.8 kW at 0.8 power factor, 0.85 kW at 0.85 and 0.9 kW at 0.9. It is 1 kW only when the power factor is 1, as with a resistive heater.
How many kVA is 1 kW?
1 kW needs 1.25 kVA at 0.8 power factor, 1.18 kVA at 0.85 and 1.11 kVA at 0.9.
How do you calculate kVAR from kW and kVA?
Use the power triangle: kVAR = √(kVA² − kW²). For 100 kVA and 80 kW, kVAR = √(10,000 − 6,400) = 60 kVAR.
What is 70 kVA in kW?
56 kW at 0.8 power factor, 59.5 kW at 0.85 and 63 kW at 0.9.
How many kW is a 125 kVA generator?
100 kW at the standard 0.8 generator power factor. A 62.5 kVA set is 50 kW and an 82.5 kVA set is 66 kW.
How do you convert HP to kVA?
kVA = HP × 0.746 ÷ (motor efficiency × power factor). A 10 HP motor with 90 % efficiency and 0.85 power factor needs 10 × 0.746 ÷ (0.9 × 0.85) = 9.75 kVA. Use the HP to kW calculator for the first step.
How many kW is a 100 kVA generator?
80 kW. Generators are rated at 0.8 power factor, so kW = 100 × 0.8. Check whether the 100 kVA figure is a standby or prime rating.
What is 500 kVA in kW?
400 kW at 0.8 power factor, 425 kW at 0.85 and 450 kW at 0.9. At 400 V three-phase, 500 kVA is a full-load current of about 722 A.
What is 1000 kVA in kW?
800 kW at 0.8 power factor, 850 kW at 0.85 and 900 kW at 0.9.
Is the kVA to kW formula different for three-phase?
No. kW = kVA × PF for both single-phase and three-phase. The phase only matters when you convert power to current.
What power factor should I use?
Use the nameplate or a measured value. Generator ratings use 0.8. Loaded induction motors are often between 0.8 and 0.9, and resistive heaters are close to 1. Lightly loaded motors can be much lower.
Why are generators and transformers rated in kVA and not kW?
Their heating depends on the current and voltage they carry, not on how much of that power does useful work. The manufacturer does not know the power factor of your load, so the rating is given in kVA.
Is this a final design or equipment approval?
No. The result is a conversion for planning and checking. Confirm generator, transformer and UPS sizing with the manufacturer data, including motor starting, harmonics and site conditions.
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