AC Power Calculator

• •Use the AC Power Calculator to check your hand calculations on homework or exam problems — comparing its result with your own working helps identify arithmetic errors before they propagate.
• •Use it during the early design phase to rapidly iterate on parameters and narrow down feasible configurations before committing time to detailed finite element simulations or full design packages.
• •Use it when reviewing a colleague's calculation or checking a vendor's data sheet for plausibility — a quick sanity check can prevent costly downstream errors.
• •Use it to generate reference data for a technical report or presentation without manual computation, ensuring consistent, reproducible numbers throughout the document.
• •Use it in the field when a quick estimate is needed and a full engineering software package is not available.

The AC Power Calculator is a precision engineering calculation tool designed for students, engineers, and technical professionals. Real, reactive, and apparent power; power factor; power triangle for AC circuits with leading/lagging identification All calculations are performed using established engineering formulas from the relevant scientific literature and standards. Follow the units printed beside each field. Where a unit selector is provided, the selected unit is converted internally. Results are computed in your browser without sending data to a server, which keeps your inputs private. This calculator is intended as a supplementary tool for learning and design exploration; always verify results against authoritative references for safety-critical applications.

In AC circuits with reactive loads, real power P (watts, dissipated as heat or work), reactive power Q (volt-amperes reactive, stored and returned), and apparent power S (volt-amperes, the total 'carried' by the line) are related by the power triangle: S² = P² + Q². The power factor PF = cos(φ) = P/S, where φ is the phase angle between voltage and current. For purely resistive loads, PF = 1 and all apparent power is real. For purely inductive or capacitive loads, PF = 0 and all apparent power is reactive (nothing dissipates). Real loads fall in between, typically 0.7-0.95 for industrial facilities. Lagging PF is caused by inductive loads (motors, transformers); leading PF is caused by capacitive loads (capacitor banks, long cables). Utility companies charge for apparent power consumption and often penalize poor power factor because it requires higher line current (and hence larger transformers, larger conductors, and more losses) for the same useful work. Power factor correction adds capacitors in parallel with inductive loads to cancel their reactive power, raising PF toward unity. The calculator takes the RMS voltage and current with either the phase angle or the power factor (and whether the load leads or lags), and computes P, Q, S, PF, and the phase angle.

• •Industrial power factor correction: install capacitor banks to improve PF from 0.7 to 0.95+, reducing utility charges and freeing capacity on transformers.
• •Motor sizing: compute apparent power S from motor rated real power and PF to size conductors, circuit breakers, and transformers correctly.
• •UPS and generator sizing: specify apparent power rating (kVA) for backup power to handle inductive loads even though only real power matters for energy calculation.
• •Transformer selection: transformer capacity is rated in kVA because heating depends on current (I² × R losses), not just active power.
• •Three-phase system analysis: wye and delta connections require vector-based power analysis with per-phase and total power calculations.