3 phase power calculator
Enter line-to-line voltage, current and power factor to see real, apparent and reactive power. Or switch to solve for the current a kW load will draw.
Three-phase power formulas
P (kW) = 1.732 × VLL × I × PF ÷ 1000S (kVA) = 1.732 × VLL × I ÷ 1000Q (kVAR) = √(S² − P²)VLL is the voltage between any two phases (208, 240, 480 or 600 V in North America; 400 V in much of the world). Line-to-neutral voltage is VLL ÷ 1.732, which is why a 208Y/120 V system has 120 V receptacles.
Worked example
A 480 V motor drawing 50 A at 0.9 PF: P = 1.732 × 480 × 50 × 0.9 = 37.4 kW. Apparent power is 41.6 kVA, reactive power 18.1 kVAR.
These formulas assume a balanced load (equal current on all three phases). For unbalanced loads, add up the power on each phase separately using line-to-neutral voltage.
Questions people ask
What is the 3-phase power formula?
P (W) = √3 × VLL × I × PF. Apparent power S (VA) = √3 × VLL × I. Reactive power Q = √(S² − P²).
Why √3?
In a balanced three-phase system the line-to-line voltage is √3 times the line-to-neutral voltage. Total power is 3 × VLN × I × PF, which equals √3 × VLL × I × PF.