Power factor is real power divided by apparent power: PF = P ÷ S. A load drawing 3 kW of real power and 5 kVA of apparent power has a power factor of 0.60, a phase angle of 53.13° and 4 kVAR of reactive power. From a meter reading, S is volts times amps, multiplied by √3 on three-phase supplies.
Electricians, plant engineers and students sizing cables or checking a utility bill often need the power factor of a load. Enter real power and apparent power directly, or enter the wattmeter reading with the supply voltage and current, choosing single- or three-phase. The calculator returns the power factor, the same value as a percentage, a rating band, the phase angle, the reactive power in kVAR and the apparent power, plus the working and a scale showing where the result sits. It assumes sinusoidal voltage and current, so on loads with heavy harmonic distortion, such as cheap switch-mode supplies, the figure is the true power factor only if your real power reading comes from a true-RMS wattmeter.
Choose kW and kVA if you have both powers, or watts, volts and amps if you have meter readings.
For volts and amps, choose single-phase or three-phase; three-phase uses line-to-line voltage.
Type the real power and the other quantities; the result updates as you type.
Check the phase angle and kVAR to see how much reactive power the load circulates.
Result Power factor: 0.600
Power factor as a percentage: 60%
Rating: Poor (below 0.80)
Phase angle φ (degrees): 53.13
Reactive power Q (kVAR): 4
Apparent power S (kVA): 5
A motor load reading 3 kW on the wattmeter but 5 kVA of apparent power runs at a power factor of 0.6, with 4 kVAR circulating as reactive power.
Result Power factor: 0.900
Power factor as a percentage: 90%
Rating: Good (0.90 to 0.95)
Phase angle φ (degrees): 25.84
Reactive power Q (kVAR): 0.501
Apparent power S (kVA): 1.15
A single-phase appliance drawing 5 A at 230 V while a power meter reads 1035 W has a power factor of 0.90.
Result Power factor: 0.800
Power factor as a percentage: 80%
Rating: Poor (below 0.80)
Phase angle φ (degrees): 36.91
Reactive power Q (kVAR): 4.16
Apparent power S (kVA): 6.928
On a 400 V three-phase supply, 10 A per line and 5.54 kW of real power work out to a power factor of about 0.80.
PF = P ÷ S; S = V × I (single-phase) or √3 × V × I (three-phase); Q = √(S² − P²); φ = arccos(PF)
PSQV, IφReal, reactive and apparent power form a right triangle, with S as the hypotenuse. Power factor is the cosine of the angle between S and P. Real power cannot exceed apparent power, so the tool rejects inputs where P is larger than S. The rating bands are rules of thumb used in industry; many tariffs penalise values under about 0.90.
Most industrial tariffs treat 0.95 or above as excellent and expect at least 0.90. Below 0.80 the extra current heats cables and transformers noticeably, and utilities often add a reactive-power charge.
Apparent power is the hypotenuse of the power triangle, so it is always at least as large as real power. If your readings show otherwise, one meter is wrong or the values are in different units.
For a balanced three-phase load, S = √3 × line-to-line voltage × line current. At 400 V and 10 A that is 6,928 VA, or about 6.93 kVA.
It is the angle by which current lags or leads voltage. A power factor of 0.9 corresponds to about 25.8°, and 0.6 to about 53.1°. Zero degrees means a purely resistive load.
Inductive loads such as motors draw lagging reactive power. Capacitors supply leading reactive power locally, which cancels part of Q, shrinks S and raises P ÷ S without changing the real work done.
Residential meters usually bill only kWh of real energy, so a low power factor rarely appears on a household bill. It matters more for commercial and industrial customers whose tariffs include kVA or kVARh charges.
Using this tool in an assignment, article or report? Copy a citation, or a link for your website.
Tools Directory Editorial Team. (2026, October 12). Power Factor Calculator. Tools Directory. Retrieved October 25, 2026, from https://tools.milunir.com/electronics-physics/power-and-energy/power-factor-calculator/
Tools Directory Editorial Team. “Power Factor Calculator.” Tools Directory, 12 Oct. 2026, https://tools.milunir.com/electronics-physics/power-and-energy/power-factor-calculator/. Accessed 25 Oct. 2026.
Tools Directory Editorial Team. “Power Factor Calculator.” Tools Directory. Last modified October 12, 2026. Accessed October 25, 2026. https://tools.milunir.com/electronics-physics/power-and-energy/power-factor-calculator/.
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