Power Factor Calculator
Enter a load's real power and its current power factor (or the voltage and current), pick a target, and get the reactive compensation in kVAR plus the single-phase capacitor size in µF.
This power factor calculator sizes the correction capacitor a load needs to reach a better power factor. Enter the real power in kW and either the present power factor or the measured voltage and current, then set a target such as 0.95. It runs the power factor correction and returns the reactive compensation in kVAR and, for a single-phase supply, the capacitor value in microfarads. Use it as a quick pf correction calculator before you spec a capacitor bank. Everything runs in your browser, nothing uploaded.
Load
Correction needed
55.32 kVAR
2,547.7 µF capacitor (single-phase)
- Current power factor
- 0.75
- Target power factor
- 0.95
- Phase angle before
- 41.41°
- Phase angle after
- 18.19°
- Apparent power before
- 133.33 kVA
- Apparent power after
- 105.26 kVA
Correcting the power factor shrinks the apparent power (kVA) the supply must carry, so the same real work draws less current. The capacitor bank supplies the reactive power locally instead of pulling it from the utility.
The µF figure assumes a single-phase capacitor across the supply voltage. For a three-phase bank the per-phase capacitance depends on the delta or wye connection, so size the bank in kVAR and have an electrician confirm the switching steps.
How it works
- 1
Enter the load
Type the real power in kW, then give the current power factor directly or switch to volts and amps to derive it.
- 2
Set the target
Choose the power factor you want to reach, add the system voltage and pick 50 or 60 Hz for the capacitor size.
- 3
Read the correction
See the kVAR the capacitor bank must supply and the single-phase µF, plus the phase angle and kVA before and after.
Instant & 100% private — nothing is uploaded
Every calculation runs locally in your browser. The income, balances and goals you enter stay on your own device and are never sent to a server — nothing is stored, logged or shared.
Frequently asked questions
- How is the required kVAR calculated?
- It uses Qc = P × (tan φ1 − tan φ2), where φ1 and φ2 are the phase angles before and after correction, taken from the current and target power factors. For 100 kW going from 0.7 to 0.95 that is about 69.1 kVAR.
- How do I size the capacitor in microfarads?
- For a single-phase supply the tool uses C = Qc × 10⁹ / (2π f V²), with Qc in kVAR, f the supply frequency and V the system voltage. Enter the voltage and frequency and the µF appears next to the kVAR.
- I don't know my power factor. Can I still use it?
- Yes. Switch the input to volts and amps. The calculator reads apparent power as V × I, then divides your real power by it to get the current power factor before working out the capacitor pf correction.
- What target power factor should I aim for?
- Most utilities want 0.95 or better to avoid a low-power-factor penalty. Correcting all the way to unity (1.0) can cause leading-power-factor problems at light load, so 0.95 to 0.98 is the usual goal.
- Does this work for a three-phase capacitor bank?
- The kVAR figure is correct for any system, but the microfarad value assumes a single-phase capacitor across the supply voltage. A three-phase bank splits the kVAR across three capacitors whose µF depends on a delta or wye connection, so size it in kVAR and have an electrician set the µF.
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