Power Factor Calculator
Calculate power factor, reactive power, and phase angle for motors and other AC loads. Understand the efficiency impact on your system.
How to Use This Calculator
Choose your input method
Select whether to calculate from real watts + apparent VA (if you have both values from a spec sheet) or from voltage + current measurements (from a clamp meter). For V&I mode, also enter the real watts if known — otherwise the calculator assumes 0.8 PF.
Enter your values
For the power input method: real power (W) is what the device spec sheet lists as power consumption or what a true-watt meter reads. Apparent power (VA) is voltage × current, found on UPS units, motor nameplates, and generator ratings. For motors, the nameplate kVA rating is apparent power.
Read the results
The result shows your power factor (0 to 1.0), reactive power in VAR, phase angle in degrees, and the efficiency impact — how much more current (and thus wiring losses) result from operating at your PF versus an ideal PF of 1.0.
The Formula
Power factor represents how efficiently current is being used to do real work. A PF of 0.8 means 80% of the apparent power (VA) is doing useful work; the remaining 20% is reactive power circulating in the system. This reactive power doesn't do work but does flow through wires and transformers, causing extra heating and losses.
Example
Three-phase AC unit — understanding PF impact
A commercial AC unit draws 2,000 VA at 1,400W real power. What is the power factor and efficiency impact?
Efficiency impact
At PF 0.70, the AC unit draws 43% more current than a purely resistive 1,400W load would. This doubles the resistive wiring losses and means you need larger wire to avoid excessive voltage drop. A power factor correction capacitor bank could bring PF to 0.95+, reducing current draw and losses significantly — cost-effective for commercial installations with multiple motor loads.