Categories⚡ Engineering & EnergyElectrical Power Calculator

Electrical Power Calculator

Calculate electrical power (P=VI), current, voltage, and circuit resistance.

Calculated Real Power (P)
24 W
Guide & Educational Reference
How to Use the Electrical Power Calculator
  1. 1Select your calculation mode: DC Power, Resistive Circuit, AC Single Phase, or AC Three Phase.
  2. 2Enter the required parameters for the selected mode (Voltage, Current, Resistance, or Power Factor).
  3. 3Review the real power (W) and, for AC modes, apparent power (VA) and reactive power (VAR).
Understanding Electrical Power Modes

Electrical power measures the rate at which electrical energy is transferred by an electric circuit. Depending on whether the circuit operates on direct current (DC), pure resistive load, or alternating current (AC single/three phase), power calculations involve real power (W), apparent power (VA), and reactive power (VAR).

Formulas Implemented by Mode
1. DC Power (P = V × I)

Direct current power calculation.

P = V × I (Real Power in Watts)
2. Resistive Circuit (P = V² / R)

Calculates power and current from voltage and resistance.

P = V² / R (Real Power in W) | I = V / R (Current in A)
3. AC Single Phase (P = V × I × PF)

Includes Power Factor (PF), Apparent Power (S), and Reactive Power (Q).

P = V × I × PF (W) | S = V × I (VA) | Q = √(S² − P²) (VAR)
4. AC Three Phase (P = √3 × V × I × PF)

Three-phase balanced AC power calculation.

P = √3 × V × I × PF (W) | S = √3 × V × I (VA) | Q = √(S² − P²) (VAR)
Practical Real-World Example
AC Single Phase Motor (120 V, 10 A, PF 0.8)
P = 120 × 10 × 0.8 = 960 W | S = 120 × 10 = 1200 VA | Q = √(1200² − 960²) = 720 VAR
→ Real Power = 960.00 W | Apparent Power = 1,200.00 VA | Reactive Power = 720.00 VAR
DC mode: 12 V and 2 A
P = V × I = 12 × 2
→ 24 W real power
AC single-phase: 230 V, 5 A, power factor 0.8
Apparent = 230 × 5 = 1150 VA; Real = 1150 × 0.8 = 920 W; Reactive = √(1150² − 920²) ≈ 690 VAR
→ 920 W, 1,150 VA, ≈ 690 VAR
Important Considerations & Units
  • Power Factor (PF) range: Must be between 0.0 and 1.0. Entering a value outside this range displays an error.
  • Units explained: Watts (W) = useful real work performed; Volt-Amperes (VA) = total power supplied; Volt-Amperes Reactive (VAR) = reactive power stored in magnetic/electric fields.
  • Resistive mode division: Resistance must be greater than zero (R > 0) to avoid division by zero.
Frequently Asked Questions

What is the difference between real power (W) and apparent power (VA)?

Real power (Watts) is the actual energy consumed to perform work. Apparent power (VA) is the total product of RMS voltage and current supplied to an AC circuit.

Why does Three-Phase power include √3 (approx. 1.732)?

In a balanced three-phase system, line voltage and line current are phase-shifted by 120 degrees, producing a total power multiplier of √3.

What do the modes do?

DC uses P = V × I. Resistive uses P = V²/R or P = I²·R. AC single-phase multiplies apparent power (V × I) by the power factor; AC three-phase multiplies by √3 × V × I × power factor.

What range is the power factor?

Between 0 and 1. A value of 1 means purely resistive load where real power equals apparent power.

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