Three-Phase Power Calculator
Convert voltage, current and power factor into apparent, active and reactive power with the correct single- or three-phase relationship.
Calculation method
For three-phase systems the calculator uses S = √3 × U × I. For single-phase systems it uses S = U × I. Active power is P = S × PF and reactive power is Q = √(S² − P²). The phase angle is acos(PF). Values are reported in kVA, kW and kVAr.
How to use the result
Use the calculator for quick load conversions, motor or equipment sanity checks and for comparing measured current with expected power. The result is most useful when voltage and current are RMS values and the power factor represents the actual combined displacement and distortion behaviour relevant to the measurement.
Engineering limits
The equations assume a balanced three-phase system when three-phase mode is selected. They do not calculate phase-by-phase imbalance, harmonic apparent power or sequence components. For nonlinear loads, verify how the measurement instrument defines PF, kVA and harmonic power quantities.
Before design release
Record the source and revision of every project input used in this calculation, then compare the result with the next practical equipment or conductor size rather than treating the numerical minimum as an automatic selection. Check tolerances, environmental derating, duty cycle, protection settings, installation constraints and manufacturer limits that are outside the simplified model. Where the result feeds another study, carry the same voltage, current, power-factor, fault-level and timing assumptions forward so the design chain remains traceable. Save the governing case and the reason for the final engineering choice. ElectroDesigner is intended to make the calculation path visible; it does not replace the project engineer’s verification, the adopted standard or tested manufacturer data.