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Power Factor Calculator
Select your current type (AC – Single phase or AC – Three phase), input the real power in kilowatts, the current in amps, the voltage in volts, the frequency in hertz, and the corrected power factor. Click the "Calculate" button to see the power factor result, apparent power, reactive power, and the required correction capacitor value.
How Do I Calculate Power Factor?
The power factor (PF) measures how efficiently electrical power is being used in an AC circuit. It is the ratio of real (useful) power consumed by a load to the apparent power drawn from the supply. A power factor of 1 (or 100%) means all the power is being used productively, while a lower value indicates wasted energy in the form of reactive power. Industries and utilities strive to maintain a high power factor to reduce electricity costs and improve grid efficiency.
Power factor is defined as the cosine of the phase angle (θ) between voltage and current waveforms. Reactive loads such as induction motors, transformers, and fluorescent lighting cause the current to lag or lead the voltage, reducing the power factor. Correction is achieved by adding capacitor banks in parallel with the load.
Core Formulas
Single-phase apparent power:
Three-phase (line-to-line) apparent power:
Three-phase (line-to-neutral) apparent power:
Initial reactive power:
Corrected apparent power:
Corrected reactive power:
Reactive power needing correction:
Required correction capacitor:
How to Use This Calculator
- Choose Current Type — Select AC Single phase for home appliances, or AC Three phase (Line-to-Line / Line-to-Neutral) for industrial equipment.
- Enter Real Power (kW) — Input the actual power consumed by your load as shown on the appliance nameplate or energy meter.
- Enter Current (Amps) — Provide the measured RMS current flowing through the circuit using a clamp meter or nameplate data.
- Enter Voltage (Volts) — Type in the supply voltage (e.g., 230 V for single phase, 400 V for three phase line-to-line).
- Enter Frequency (Hz) — Most countries use 50 Hz; North America uses 60 Hz. Enter accordingly.
- Enter Corrected PF (0–1) — Type the target power factor you want to achieve (typically 0.95 or 0.99 for industrial applications).
- Click Calculate — Instantly see your power factor, apparent power, reactive power, and the exact capacitor size needed for correction.
- Reset if needed — Click Reset to clear all fields and start a new calculation.
Real Calculation Example
Let's consider a household appliance operating in a single-phase AC circuit. Suppose the appliance has a real power consumption of 3 kW, the current is 15 A, the voltage is 230 V, and the frequency is 50 Hz. The corrected power factor target is 0.9.
Step 1 – Apparent power:
S = V × I = 230 × 15 = 3450 VA = 3.45 kVA
Step 2 – Initial power factor:
PF = P ÷ S = 3 ÷ 3.45 ≈ 0.87
Step 3 – Corrected apparent power:
Scorrected = 3 ÷ 0.9 ≈ 3.3333 kVA
Step 4 – Initial reactive power:
Q = √(3.45² − 3²) ≈ 1.7037 kVAR
Step 5 – Corrected reactive power:
Qcorrected = √(3.3333² − 3²) ≈ 1.4529 kVAR
Step 6 – Reactive power needing correction:
Qc = 1.7037 − 1.4529 = 0.2508 kVAR
Step 7 – Correction capacitor:
C = 10⁹ × 0.2508 ÷ (2 × π × 50 × 230²) ≈ 15.09 μF
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