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Three-Phase Power Calculator

Enter line-to-line voltage, line current and power factor for a balanced three-phase load.

V
A

Real power

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Apparent power
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Equivalent horsepower
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Reactive power
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Tips for using the three-phase power calculator

  • Use line-to-line voltage, not line-to-neutral (480 V, not 277 V).
  • For unbalanced loads, calculate each phase separately and add.
  • Size conductors and protection from the motor nameplate current and the NEC tables, not this estimate alone.

How the three-phase power calculator works

A balanced three-phase system delivers power on three conductors whose voltages are 120° apart. Total power uses the line-to-line voltage and √3, which comes from the geometry of the three phases.

S (kVA) = √3 × VLL × I ÷ 1,000
P (kW) = S × power factor
Current I = P × 1,000 ÷ (√3 × V × PF)

Common US three-phase voltages are 208 V, 240 V and 480 V. The horsepower figure is electrical input divided by 746 W/hp; a motor's shaft output is lower because of its efficiency, typically 90% to 96% for modern premium-efficiency motors.

Worked example

A 480 V motor drawing 50 A at 0.85 power factor uses √3 × 480 × 50 = 41.57 kVA of apparent power and 41.57 × 0.85 = 35.33 kW of real power, about 47.4 hp of electrical input. Reactive power is 21.9 kVAR.

Frequently asked questions

Why is √3 used in three-phase power?

Because line-to-line voltage is √3 times the phase voltage in a wye system, and phase currents are 120° apart.

How do I convert kW to amps in three-phase?

Amps = kW × 1,000 ÷ (√3 × volts × PF).

What is the difference between kW and kVA?

kW is real power; kVA is apparent power. kW = kVA × power factor.

Is 208 V three-phase the same as 240 V?

No. 208 V comes from a 120/208 V wye system; 240 V usually from a delta system.

Updated October 2026. Results are estimates for education, not financial or medical advice. All math runs in your browser; nothing you type is sent anywhere.

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