Power-factor correction calculator
Explore the theoretical reactive compensation needed to improve a lagging power factor while keeping active power constant.
Educational reference only. Examples and calculator results are not approved installation designs, equipment selections or operating instructions.
Your inputs
Results update as you edit. Use a decimal point. Default values are hypothetical, not recommended equipment sizes.
Electrical input or load power, not motor shaft output.
Enter a positive power factor up to 1, for example 0.9.
Enter a positive power factor up to 1, for example 0.9.
Illustrative result
- Theoretical compensation
- 138.308 kvar
- Initial apparent power
- 333.333 kVA
- Target apparent power
- 263.158 kVA
Worked steps
- tan(φinitial) = tan(acos(0.75)) = 0.882
- tan(φtarget) = tan(acos(0.95)) = 0.329
- Qc = 250 × (0.882 − 0.329) ≈ 138.308 kvar
Calculations use unrounded values; displayed steps are rounded to three decimal places or five significant digits for extreme values.
Formula and units
Qc (kvar) = P × [tan(acos(PFinitial)) − tan(acos(PFtarget))]
Change one input to see its effect. Inputs are calculated in your browser and are not submitted to a calculation service.