Power Factor Calculator
Solve kW, kVA, kVAR and power factor from the values you have, or calculate the capacitive kVAR needed to improve a lagging load.
How to Use
- Choose the values you have - start with kW+kVA, kW+kVAR, kVA+kVAR, kW+known PF, or measured kW+volts+amps. The calculator fills in the remaining power-triangle values.
- Label leading or lagging separately - power factor magnitude alone does not tell you reactive direction. Use lagging for inductive loads and leading for capacitive direction when that is known.
- Use correction mode only for lagging loads - enter kW, current lagging PF, and target PF. Voltage is optional and adds line-current and ideal-capacitance context.
- Treat µF as an ideal equivalent - real capacitor-bank selection depends on rated voltage, frequency, switching, harmonics, resonance, tolerance, duty, protection, and manufacturer data.
Electrical power factor is PF = kW ÷ kVA = cos φ for the sinusoidal/displacement power triangle. A 75 kW load drawing 90 kVA has PF ≈ 0.8333, reactive-power magnitude ≈ 49.75 kVAR, and phase-angle magnitude ≈ 33.56°. A 100 kW lagging load corrected from PF 0.80 to 0.95 needs about 42.13 kVAR of capacitive correction.
The Electrical Power Triangle
Solve Power Factor From the Values You Have
Different meters, nameplates, and studies provide different combinations of kW, kVA, kVAR, voltage, current, and PF. Choose the mode that matches the values in front of you and the calculator returns the remaining power-triangle quantities.
For measured voltage/current mode, single-phase apparent power is V × I and balanced three-phase apparent power is √3 × VLL × I. Real kW divided by that kVA gives the power-factor magnitude.
The formulas describe the sinusoidal/displacement power triangle. Nonlinear loads can have distortion power factor, so a power-quality analyzer may report total PF that cannot be reconstructed from a simple phase angle alone.
If several equipment loads need to be combined before you evaluate the aggregate power relationship, use the Electrical Load Calculator first to total the known W or VA values.
Power Triangle Examples
| Real power | Apparent power | Power factor | Reactive-power magnitude |
|---|---|---|---|
| 50 kW | 50 kVA | 1.000 | 0 kVAR |
| 50 kW | 62.5 kVA | 0.800 | 37.5 kVAR |
| 75 kW | 90 kVA | 0.833 | 49.75 kVAR |
| 100 kW | 111.11 kVA | 0.900 | 48.43 kVAR |
Reactive magnitude is Q = √(S² − P²). Lagging/leading direction is a separate property.
Power-Factor Correction
For a lagging inductive load, correction kVAR is calculated from Qc = P × (tan φ1 − tan φ2), where φ1 = arccos(PF1) and φ2 = arccos(PF2). Real kW stays constant while reactive demand, apparent kVA, and line current fall.
If system voltage is entered, correction mode also compares line current before and after. It additionally reports the correction-bank line-current magnitude and an ideal capacitance equivalent for the chosen frequency. For three-phase banks, Delta and Wye capacitance are different because individual capacitors see different voltages.
That ideal µF value is not a purchase recommendation. Harmonics, resonance, switching steps, load variation, system short-circuit strength, capacitor voltage rating, tolerances, and manufacturer application guidance can require a detuned, filtered, automatic, or otherwise engineered system.
Power-Factor Correction Multiplier Reference
| Current PF | To 0.90 PF | To 0.95 PF | To 0.98 PF |
|---|---|---|---|
| 0.60 | 0.849 kVAR/kW | 1.005 kVAR/kW | 1.130 kVAR/kW |
| 0.65 | 0.685 | 0.840 | 0.966 |
| 0.70 | 0.536 | 0.692 | 0.817 |
| 0.75 | 0.398 | 0.553 | 0.679 |
| 0.80 | 0.266 | 0.421 | 0.547 |
| 0.85 | 0.135 | 0.291 | 0.417 |
| 0.90 | N/A | 0.156 | 0.281 |
Multiply load kW by the factor to estimate required capacitive kVAR. Values are formula-derived from tan(arccos(PFcurrent)) − tan(arccos(PFtarget)); a dash means the listed target is not above the current PF.
Worked Correction Example: 100 kW, PF 0.80 → 0.95
| Quantity | Before | After / correction |
|---|---|---|
| Apparent power | 125.00 kVA | 105.26 kVA |
| Reactive power | 75.00 kVAR | 32.87 kVAR |
| Capacitive correction | N/A | 42.13 kVAR |
| Phase angle | 36.87° | 18.19° |
| 480 V 3φ line current | 150.35 A | 126.63 A |
The line-current row assumes balanced 480 V three-phase. Actual capacitor equipment still requires application engineering.
When a Capacitor-Only Answer Needs More Review
Capacitor kVAR can be calculated from the power triangle, but that does not prove that a plain capacitor bank is suitable for the system. Nonlinear loads such as variable-frequency drives and rectifiers can interact with capacitors and system inductance at harmonic frequencies.
Eaton's plant-engineer guide uses the ratio of total three-phase nonlinear-load kVA to the main transformer kVA as a screening indicator. It says plain capacitors can usually be applied without problems below 15%, harmonic filters will almost always be required above 25%, and systems between those values need other factors considered.
Those percentages are Eaton application guidance, not a universal pass/fail rule. Harmonic measurements, system short-circuit strength, utility requirements, switching method, and equipment manufacturer guidance still control the final design.
Power Factor and Correction Formulas
The core relationships used by the calculator are:
Apparent power = kVA = √(kW² + kVAR²)
Reactive magnitude = kVAR = √(kVA² − kW²)
Phase angle = φ = arccos(PF)
Single-phase apparent power = kVA = V × I ÷ 1000
Balanced three-phase apparent power = kVA = √3 × VLL × I ÷ 1000
Correction kVAR = Qc = kW × [tan(arccos PF1) − tan(arccos PF2)]
Single-phase ideal capacitance = C = Q ÷ (2πfV²)
3φ Delta ideal capacitance per capacitor = C = Qtotal ÷ (3 × 2πfVLL²)
3φ Wye ideal capacitance per phase = C = Qtotal ÷ (2πfVLL²)
Capacitance formulas produce ideal steady-state equivalents. Real bank rating and application must follow equipment/manufacturer and system-study requirements.
Authoritative Technical Sources
- Fluke defines power factor as the ratio of working power in kW to apparent power in kVA and explains the relationship between power factor, kVA, current, and system loading.Fluke - Power Factor: What it is and How to Calculate it
- Eaton publishes the kW/kVA/kVAR relationships, current and capacitor formulas, correction method, and harmonic-screening guidance used to decide when plain capacitors may need a deeper system review.Eaton - Power factor correction: A guide for the plant engineer
- Schneider Electric provides an official power-factor-correction calculator/tool intended to estimate capacitor kVAR required to improve the power factor of a load or system.Schneider Electric USA - Power Factor Correction Calculator
Next Steps
Use the result in the next electrical calculation that needs it:
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Power factor connects real power, apparent power, reactive power, and current. Browse the electrical calculator collection for conversion, load, transformer, conductor, and protection tools.