Power Factor Calculator
A low power factor wastes energy and can add surcharges to your electricity bill. This free calculator finds the power factor of your load from kW, kVA, voltage and current — and sizes the capacitor (kVAR) needed to correct it toward your target.
Power factor correction
Result
| Power factor (cos phi) | |
|---|---|
| Phase angle | |
| Real power | |
| Apparent power | |
| Reactive power |
Capacitor correction
| Required capacitor (kVAR) | |
|---|---|
| Capacitance |
Formula: Qc = P × (tanφ1 − tanφ2), then C = Qc ÷ (2πfV²). Always use a capacitor rated above the voltage and have an electrician install it.
How to use
- Enter the known values of your load (kW/kVA or V/A/PF).
- For correction, enter the current PF, target PF, load and voltage.
- Press "Calculate" — you will get the PF, kVAR and capacitor size.
Tips
- Most utilities penalize a power factor below about 0.85 to 0.9 — correction can pay for itself.
- Measure under your normal load; a correction sized for peak load can overcorrect at light load.
- Have an electrician install the capacitor bank — mains wiring is not a DIY job.
The closer PF is to 1, the better. With a low PF, the power company may add a surcharge — confirm rates on the official website.
Frequently Asked Questions (FAQ)
What does this power factor calculator do?
It calculates the power factor of an electrical load and the capacitor size in kVAr needed to correct it toward a target power factor.
What inputs are needed?
Depending on the mode: real power in kW and apparent power in kVA for direct mode, or voltage, current and the existing power factor, with a three-phase option.
Who is it for?
Electricians, technicians and students working with motors, panels and power correction jobs.
How does it size the correction capacitor?
Enter your current power factor, target power factor, load in kW, system voltage and frequency. The tool calculates the required capacitor in kVAr and its capacitance using Qc = P times (tan of phi 1 minus tan of phi 2).
Can I install the capacitor myself?
No. The tool gives an engineering estimate only. Always use a capacitor rated above the system voltage, and have a qualified electrician install it.