Power Factor Calculator

Power factor calculator for kW, kVA, kVAR, voltage, and current

Power factor tells you how effectively an AC electrical system converts supplied electrical power into useful work. If the power factor is low, the same real power output (kW) requires more current, which increases losses, can reduce available capacity, and may trigger penalties on some utility tariffs. This calculator helps you estimate power factor using the numbers you actually have, and it also shows the related values (kVA and kVAR) so you can understand what is happening in the power triangle.

You can calculate power factor from real power (kW) and apparent power (kVA), from real power (kW) and reactive power (kVAR), or from voltage, current, and a phase angle. If you also enter a target power factor, the calculator estimates how much reactive power compensation (kVAR) would be needed to move from your current power factor to that target. This is useful for rough sizing discussions before you consult an electrician or engineer for a detailed study.

Results are shown in plain language so you can make quick decisions. You will see the power factor as a number between 0 and 1, a quality label (excellent, good, or poor), and a short practical note about what that usually means. You will also see the calculated apparent power (kVA) and reactive power (kVAR) where applicable. If you provided a target power factor, you will see an estimated kVAR correction requirement that indicates whether you would typically add capacitive or inductive compensation.

Assumptions and how to use this calculator

• All values are assumed to be steady-state RMS values for AC systems. Transients, harmonics, and non-linear loads are not modeled.
• If you calculate from kW and kVA, the calculator cannot know whether your reactive component is leading or lagging. It will label the type as unknown and assumes lagging only when estimating correction.
• If you calculate from kW and kVAR, you can choose lagging or leading. Lagging is typical for inductive loads like motors and transformers.
• Voltage and current calculations assume a sinusoidal waveform and use the phase angle to determine power factor as cos(angle). Three-phase apparent power is calculated using √3 × V × I.
• The correction estimate uses a standard approximation based on the difference between tan(arccos(PF)) values. Real installations can differ due to load variation, harmonics, switching steps, and measurement location.

Common questions

What is the difference between kW, kVA, and kVAR?

kW is real power, the part that performs useful work like turning a motor shaft or producing heat. kVA is apparent power, which reflects the total current and voltage demand on the supply. kVAR is reactive power, which oscillates between the source and the load due to inductance or capacitance and does not do net useful work, but it increases current flow.

Why does low power factor matter?

For a given kW load, a lower power factor increases the kVA required. Higher kVA generally means higher current, which can increase cable losses, heating, and voltage drop. It can also reduce how much additional load you can connect to a transformer or generator. Some utilities charge penalties or require correction for large customers.

What power factor is considered good?

Rules differ by industry and tariff, but many facilities aim for 0.90 to 0.95 or higher. Very high power factor near 1.00 is not always necessary, and over-correction (leading power factor) can create its own issues. Use the calculator to estimate where you are now, then confirm with an electrician or engineer if you plan to install correction equipment.

I only know kW and current. Can I still use this?

Yes, if you also know the voltage and whether the system is single-phase or three-phase. You can then estimate apparent power from voltage and current. However, to get an accurate power factor you also need the phase angle or a measured power factor reading from a meter. Without phase angle, any value you compute is a rough assumption, not a true measurement.

How accurate is the power factor correction estimate?

It is a planning estimate, not a final design. The calculation assumes your real power (kW) stays the same and uses a standard relationship between power factor and reactive power. Real-world loads change over time, and non-linear loads can introduce harmonics that require additional filtering or different capacitor sizing. If the estimate looks meaningful for your situation, treat it as a starting point for a proper site measurement.