Three-phase power calculator

Select wye or delta to receive the correct phase voltage and phase current as well. The total real-power formula uses line measurements, so its result is consistent for either connection when the same line voltage, line current, and power factor are supplied. Results include watts, kilowatts, volt-amperes, and kilovolt-amperes for practical design checks, equipment comparisons, and operating estimates.

Enter line measurements, not phase measurements

Use the RMS voltage measured from one supply line to another for line voltage, and use the RMS current flowing in any one supply conductor for line current. The calculator assumes a balanced three-phase load, meaning the three phase impedances and currents are equal in magnitude and separated symmetrically. Enter the power factor as a decimal between zero and one; for example, use 0.85 rather than 85. The connection selector describes how the load branches are joined. In a wye load, each phase sees line voltage divided by the square root of three, while phase current equals line current. In a delta load, each phase sees the full line voltage, while phase current is line current divided by the square root of three. These relationships let the result show useful phase quantities without asking for redundant inputs. Do not enter a phase-to-neutral voltage as line voltage, because doing so understates the total power by the square-root-of-three factor in the common wye case.

Understand the real and apparent power results

The calculator first obtains apparent power with the balanced three-phase expression S = √3 × V_L × I_L. It then multiplies apparent power by the power factor to obtain real power: P = √3 × V_L × I_L × PF. Apparent power, reported in volt-amperes and kilovolt-amperes, describes the combined voltage-current loading seen by conductors and much of the upstream equipment. Real power, reported in watts and kilowatts, is the average rate at which electrical energy is converted to useful work, heat, light, or other forms. A lower power factor produces less real power for the same line voltage and current, even though apparent power remains unchanged. The wye or delta selection does not alter total power when identical line quantities are entered; it alters the derived phase voltage and phase current. This is a useful consistency check, not an omission: both connection-specific phase formulas reduce to the same standard line-value equation for a balanced system.

Apply the result within its assumptions

Use the result for balanced motors, heaters, transformer loads, and other three-phase equipment when voltage, current, and power factor represent the same operating point. It can help compare a measured load with a nameplate rating, estimate real input power before an energy calculation, or check whether an apparent-power estimate is internally consistent. The calculation is deterministic and performs no network requests, so repeated calls with the same numeric inputs return the same values. However, it is not a substitute for a full power-quality measurement. It does not calculate reactive power, phase angle, efficiency, harmonics, voltage imbalance, current imbalance, neutral current, or transient demand. For an unbalanced installation, calculate each phase from appropriate measurements or use a three-phase power analyzer, because a single line-current value cannot represent all conductors. Also distinguish electrical input power from mechanical output power: a motor’s shaft power will be lower than its real electrical input because efficiency is less than one. The API costs $0.002 per calculation, while the browser calculation can run locally.