Engineering Tools

3-Phase Power Calculator

Calculate real, reactive and apparent power, line current, voltage, or power factor from known values.

How the calculator works

Select the values you know in box 1 and then enter them in box 2. The Calculated Values panel shows all values that can be calculated. Select a load configuration to also calculate phase voltage and phase currents.

3-Phase Power Calculator

Select your available inputs, enter their values, and see everything that can be calculated.

1. Known Inputs

Select each input that's known.

2. Known values

Enter the known inputs here to calculate the values to the right.

Select Known Inputs above to enable their entry boxes.

Example: 480 V, 1,000 kVA and 0.8 lagging power factor gives 800 kW, 600 kVAR and approximately 1,203 A.

Equations and calculation basis

Three-phase apparent power
S = √3 × VLL × IL / 1,000
S = √(P² + Q²)
Real and reactive power
P = S × PF
|Q| = S × √(1 − PF²)
Line current and voltage
IL = 1,000 × S / (√3 × VLL)
VLL = 1,000 × S / (√3 × IL)
Power factor from two power values
PF = P / S
PF = √(1 − (Q / S)²)
PF = P / √(P² + Q²)
Apparent power from power factor
S = P / PF
S = |Q| / √(1 − PF²)
Wye phase values
Vphase = VLL / √3
Iphase = IL
Delta phase values
Vphase = VLL
Iphase = IL / √3

P is real power in kW, Q is reactive power in kVAR, and S is apparent power in kVA. Voltage is in volts and current is in amperes. PF is the magnitude of cos φ, from 0 to 1. This calculator uses nonnegative real power and reports positive Q for lagging loads and negative Q for leading loads.

Power factor is undefined at zero apparent power. These equations assume balanced sinusoidal voltages and currents, they do not account for harmonics or phase imbalance. Select Load Configuration to calculate phase values. Wye or Delta changes phase values, not total power for the same line voltage and current.

When more inputs are provided than necessary, the calculator checks them for consistency. Differences greater than 0.1% are flagged; rounded entries within that tolerance are accepted.

Evaluate your power system

Power System Calcs provides short circuit studies, protective device coordination studies, and arc flash studies for commercial, industrial, and mission-critical facilities.

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