Enter a load's real power (W) and apparent power (VA). FigureDesk calculates the power factor and the reactive power implied by the two.
Your numbers
Actual work-producing power — from a meter, or watts on a nameplate.
Voltage × current — from a meter, or VA on a nameplate.
Result
Power factor
0.8
Given P = 800 W, S = 1000 VA → PF = P / S = 0.8, Q = √(S² − P²) = 600 var
Apparent power (VA) is what a source has to supply — voltage times current. Real power (W) is the portion that actually does useful work. Power factor is the ratio between them: a power factor of 1.0 means all the apparent power is doing useful work; anything less means part of the source's capacity is going toward reactive power instead, which the load draws but doesn't convert into work.
PF = P / S
Q = √(S² − P²)
A load reading 800 W real power and 1,000 VA apparent power:
Power factor is the ratio of real power (the power that actually does useful work, in watts) to apparent power (what a source has to supply, in volt-amps). A power factor of 1.0 (unity) means all the supplied power is doing useful work; anything lower means some capacity is being used to supply reactive power instead.
Many power meters and smart plugs display both directly (sometimes labeled W and VA). If you only have voltage and current, apparent power is their product (V × A); real power usually needs a meter that measures it directly, since it depends on the phase relationship between voltage and current.
A low power factor means a circuit or utility feed has to carry more current than the real power alone would require, which increases losses in wiring and equipment sizing needs. Utilities sometimes bill commercial and industrial customers for poor power factor — check your own utility's tariff for their specific threshold and penalty structure.
The kVA to kW Calculator goes the other direction: it takes a known power factor and converts between apparent power (kVA) and real power (kW). This calculator solves for the power factor itself, from real and apparent power readings you already have.
Already know your power factor? Convert between apparent power (kVA) and real power (kW) directly.
Convert power to current for a system, using a power factor if you have one.
The underlying voltage/current/power relationship for a purely resistive (PF = 1) load.
FigureDesk results are advisory and do not replace a licensed electrician, a qualified engineer, or the applicable local electrical code. Verify any electrical work against your local code and with a qualified professional before relying on it.