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Power-Factor Correction Capacitance

C=Qc2πfV2C = \frac{Q_{c}}{2\pi f V^{2}}
sig figs

Worked example: 5 kvar at 240 V, 60 Hz → 230.26 µF. Press Try an example to run it live, then adjust anything.

Enter your known values, leave one input blank, and solves for the missing one. Tap a variable’s symbol to see what it means, with a typical value. Change any unit and the answer follows.

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Q Factor of a Series Resonant CircuitRC Cutoff Frequency555 Astable Frequency
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See also

Power-Factor Correction kvar: Both use reactive power wanted.Synchronous Speed from Frequency and Poles: Both use supply frequency.555 Astable Frequency: Both use capacitance.Q Factor of a Series Resonant Circuit: Both use capacitance.RC Cutoff Frequency: Both use capacitance.Capacitance (C = Q/V): Both use voltage across the capacitor.
3 more relatedEnergy Stored in a Capacitor: Both use voltage across the capacitor.RC Capacitor Charging: Both use voltage across the capacitor.RC Capacitor Discharge: Both use voltage across the capacitor.
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Power-Factor Correction Capacitance explained

CVQcf

A capacitor's vars are Q = V²/XC, and since XC = 1/(2πfC), that rearranges to Q = 2πfCV²: solve it for C and you have your capacitor. Getting 5 kvar at 240 V and 60 Hz takes 5000/(2π × 60 × 240²) ≈ 230 µF, a physically large oil-filled can, which is why correction capacitors are bulky and why higher voltages are so much cheaper per var. The var field here uses watts: vars and watts share dimensions.

The V² is the sting. A capacitor bank rated 25 kvar at 480 V delivers only 25 × (240/480)² ≈ 6.25 kvar if someone installs it on a 240 V system: a mistake that shows up as a stubbornly unimproved power factor. Frequency matters the same way, so a bank imported from a 50 Hz country loses a fifth of its vars at 60 Hz... and gains 20% the other way, along with the overcurrent that comes with it.

Power-Factor Correction Capacitance formula

C=Qc2πfV2C = \frac{Q_{c}}{2\pi f V^{2}}
Where
  • CC= Capacitance (μF)
  • QcQ_{c}= Reactive power wanted (var) (W)
  • ff= Supply frequency (Hz)
  • VV= Voltage across the capacitor (V)
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Three-phase power and power factor

8 formulasReal, reactive and apparent power, power factor, phase angle and correction kvar — the power triangle as an electrician uses it.

Revised 16 October 2026
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formula.expert. (2026, October 16). Power-Factor Correction Capacitance Formula & Calculator. https://formula.expert/solvers/power-factor-correction-capacitance

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