Three-Phase Power Calculator

About this calculator

For a balanced three-phase system, real power is P = √3 × V_line × I × pf, where V_line is the line-to-line voltage, I is the line current, and pf is the power factor (cos θ, accounting for any phase lag between voltage and current in inductive loads like motors). The √3 factor — roughly 1.732 — comes from the 120° phase offset between the three lines, and the same relationship also gives apparent power (S = √3·V·I) and reactive power (Q = √3·V·I·sin θ).

Electricians and electrical engineers use this formula throughout industrial and commercial power work — sizing motors, transformers, and feeder cables, and calculating loads on three-phase panels — since most heavy industrial equipment runs on three-phase power rather than the single-phase supply used in homes.