Real and Reactive Power Calculator

Active and Reactive Power Estimator

Input Fields

Voltage

V

V

RMS voltage applied to the load

Current

I

A

RMS current through the load

Phase angle

φ

°

Phase angle between voltage and current

CalculateReset

Calculate automaticallyIf enabled, the result will update automatically when you change any value.

Your Results

Apparent Power

Real Power

Reactive Power

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AC Power Calculation Formulas

$$P = V \cdot I \cdot \cos(\theta)$$ $$Q = V \cdot I \cdot \sin(\theta)$$ $$S = V \cdot I$$ $$P = S \cdot \text{pf} \quad Q = S \cdot \sin(\cos^{-1}(\text{pf}))$$

Where:

• $$P$$ = real (active) power in kilowatts (kW)
• $$Q$$ = reactive power in kilovolt-amperes reactive (kVAR)
• $$S$$ = apparent power in kilovolt-amperes (kVA)
• $$V$$ = voltage (V)
• $$I$$ = current (A)
• $$pf$$ = power factor (unitless, between 0 and 1)

Real and Reactive Power – Calculation Example

Given:

• $$V$$ = 400 V
• $$I$$ = 10 A
• $$pf$$ = 0.8

Calculation:

1. $$S = \frac{400 \cdot 10}{1000} = 4~\text{kVA}$$
2. $$P = 4 \cdot 0.8 = 3.2~\text{kW}$$
3. $$\theta = \cos^{-1}(0.8) ≈ 36.87^\circ$$
4. $$Q = 4 \cdot \sin(36.87^\circ) ≈ 4 \cdot 0.6 = 2.4~\text{kVAR}$$

Real and reactive power are key elements in AC circuit analysis. Real power performs actual work (heating, motion), while reactive power maintains electric and magnetic fields in inductive or capacitive components. This calculator is vital for electrical load planning, power factor correction, and grid efficiency optimization. Whether you work on industrial systems or renewable energy, understanding these values helps manage energy flow accurately.