Electrical basics
kW to kVA calculator
Choose the direction, enter the value and the power factor, and see active, apparent and reactive power together. Generators, transformers and UPS units are rated in kVA; loads in kW.
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P: active power, Q: reactive power, S: apparent power. The lower the cos φ, the longer the Q side. Not to scale.
How is it calculated?
The ratio between active power (kW) and apparent power (kVA) is the power factor (cos φ). Reactive power follows from the power triangle.
kW to kVA
S = P / cos φ
P: active power (kW), S: apparent power (kVA), cos φ: power factor.
kVA to kW
P = S × cos φ; Q = S × sin φ
Q: reactive power (kVAr), sin φ = √(1 − cos² φ).
Example
- kW to kVA: P = 100 kW, cos φ = 0.8 → S = 125 kVA, Q = 75 kVAr.
- kVA to kW: S = 630 kVA, cos φ = 0.9 → P = 567 kW, Q ≈ 274.6 kVAr.
The example inputs are for illustration only; they are not verified defaults. Results are approximate and do not replace engineering advice.
Frequently asked questions
What is the difference between kW and kVA?
kW is the active power that does useful work. kVA is the apparent power from voltage times current and also includes reactive power. Their ratio is the power factor.
What if cos φ = 1?
Reactive power is zero and kW equals kVA. Real installations usually run below 1 because of motors and electronic loads.
Which value matters when choosing a generator?
Generators are usually rated in kVA. Knowing the kW of your load and its power factor gives the kVA equivalent; starting currents and reserve still need an engineering review.