Three-Phase Power Calculator
Compute real power delivered by a balanced three-phase supply.
Formula
P = √3 × VL × IL × PF
Inputs
- Line voltage (VL) (V)
- Line current (IL) (A)
- Power factor
What it does
Real power delivered by a balanced three-phase supply: P = √3 × V_L × I_L × PF.
Where it's used
Motors, industrial loads and sizing three-phase supplies.
How to use it
- Enter the line-to-line voltage.
- Enter the line current.
- Enter the power factor (from the nameplate or a meter).
The formula explained
- V_L
- line-to-line voltage
- I_L
- line current
- PF
- power factor (cos φ)
- √3
- about 1.732, from the 120° phase spacing
Worked example
Inputs:
- Line voltage (VL): 415 V
- Line current (IL): 32 A
- Power factor: 0.85
The calculator gives:
- Result: 19.551 kW
- Power (Watts): 19551.4 W
Tips and common mistakes
- Use line-to-line voltage (e.g. 400 or 415 V), not phase voltage.
- Only valid for balanced loads.
- For apparent power (kVA), set PF = 1.
Questions people ask
How do I find the current from the power?
I = P / (√3 × V_L × PF). An 11 kW motor on 415 V with a power factor of 0.85 draws about 18 A per line.
What is the difference between line and phase voltage?
Line voltage is measured between two phases; phase voltage between a phase and neutral. In a star system V_L = √3 × V_ph, so 230 V phase voltage gives about 400 V between lines.
Why is three-phase used for big loads?
It delivers power smoothly instead of in pulses, needs less copper than single-phase for the same power, and gives motors a rotating magnetic field so they start and run without extra parts.
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Enter your values to get the result with the formula, substituted values and an explanation of each step.