EleCanada
Loads and electrical power

Power factor correction calculator

Calculate the capacitive reactive-power amount between a load's current and target lagging power factor. The result is an arithmetic quantity, not equipment selection.

Calculation inputs

Load and power-factor inputs

kW
%
%

Enter real electrical input power and lagging power-factor percentages from the same load condition. For example, enter 85 for 85%.

Enable JavaScript to calculate. The formula and scope remain below.

Reactive power

Enter a load and a target power factor.

A calculated kVAr quantity does not specify a capacitor bank, switching arrangement, protection or installation approval.

What it calculates

The calculator estimates how much capacitive reactive power would offset the change between two supplied lagging power factors while real load power remains constant.

Use measured electrical input kW and power-factor values for the same load and operating condition. Enter each power factor as a percentage from greater than 0% through 100%; the target must be at least the current value.

Method and example

For real power P and power factor PF, the reactive-power magnitude is Q = P × √(1 − PF²) ÷ PF. Required correction is the initial reactive-power magnitude minus the target reactive-power magnitude. The tool converts entered percentages to ratios before calculating.

For 100 kW at 75% lagging power factor, targeting 95% gives about 88.192 kVAr initially, 32.868 kVAr at the target, and 55.323 kVAr of calculated correction.

Limits and interpretation

The calculation assumes a steady real-power load, sinusoidal quantities, and lagging power factor represented by the supplied values. A meter's true power factor on a distorted waveform may not fit this model.

The result is not a capacitor-bank rating or design. It does not model changing loads, resonance, harmonics, switching transients, system impedance, voltage rise, protection, utility billing, or equipment limits. Confirm the actual installation and utility requirements with the relevant qualified professional.

No universal target, savings, pass/fail threshold, utility acceptance or code conclusion is applied.

Common questions

Why must the target be no lower than the current factor?

This tool calculates capacitive correction only. A lower target would increase the reactive-power requirement rather than correct the supplied starting condition.

Does the result tell me which capacitor to install?

No. The arithmetic does not select a capacitor rating, bank arrangement, switching method, protection or installation location.

Can I use total kVA or motor shaft power as the real power?

Use electrical input power in kW for the same operating point. Motor shaft output and apparent power are different quantities.

These calculators report other electrical quantities and do not select compensation equipment.

Electrical relationshipsSolve DC quantities, convert AC power/current, compare PF current ratios, or relate balanced wye voltages.Motor currentConvert mechanical shaft power or estimate motor current from matching full-load data.Connected loadTotal loads sharing a voltage, phase and power factor.

Sources

Eaton Canada, Power Factor Correction: A Guide for the Plant Engineer, document SA02607001E, effective August 2014, printed pp. 12–13, including Table 6's 75%-to-95% multiplier. Checked November 10, 2026. Its plant-engineering and equipment guidance is not implemented.

The guide's plant-engineering examples provide industrial context; they do not establish residential use, a universal correction target, a capacitor-bank design or equipment approval.

Report a problem or suggest a source. Calculation values are not included automatically.