Power Factor Calculator

What is Power Factor?

In AC circuits with reactive loads (motors, transformers, fluorescent lighting), voltage and current are out of phase. The power factor (PF) measures how efficiently electrical power is converted to useful work. A PF of 1.0 is perfect; most industrial loads have PF between 0.7–0.95.

Power Factor Formulas

PF = Real Power (W) / Apparent Power (VA) PF = cos(φ) where φ is the phase angle between voltage and current

Power relationships:

• Apparent Power (S) in VA = V × I
• Real Power (P) in W = V × I × PF
• Reactive Power (Q) in VAR = V × I × sin(φ) = √(S² − P²)

How to Use This Calculator

Enter any two of: real power (W), apparent power (VA), or reactive power (VAR). Or enter voltage, current, and phase angle. The calculator returns PF, all three power types, and the correction capacitor size needed.

Practical Examples

Example 1: Motor draws 10A at 230V, consuming 1,800W. Apparent = 2,300VA. PF = 1,800/2,300 = 0.78 lagging.

Example 2: Data centre with 100kW load at PF 0.85. Apparent power = 100/0.85 = 117.6 kVA — this is the transformer and UPS capacity needed.

Why Power Factor Matters

Low power factor means more current for the same real power, increasing cable and transformer losses. Utilities charge industrial customers penalty tariffs for PF below 0.9. Power factor correction capacitors reduce reactive power and bring PF closer to 1.0.