Calculate electrical power, current, voltage, and resistance with power factor correction, 3-phase support, energy cost analysis, and wire sizing.
The electrical power calculator computes power, current, voltage, and resistance using the fundamental power equations P = IV, P = I²R, and P = V²/R. It supports both single-phase and three-phase AC systems with power factor correction, providing a complete picture of real, apparent, and reactive power in the power triangle.
Understanding electrical power relationships is essential for circuit design, load planning, energy management, and electrical safety. This calculator goes beyond simple P = IV by including power factor effects that separate real power (watts) from apparent power (VA) — critical for sizing transformers, generators, and conductors in AC circuits. For three-phase systems, it applies the √3 factor that accounts for the three balanced voltage phases.
The tool also provides practical outputs including recommended wire gauge per NEC standards, daily and monthly energy costs, BTU/hr heat output, and a load scaling table. Whether you're planning a home electrical circuit, sizing an industrial motor feeder, or calculating the operating cost of equipment, this calculator delivers all the answers in one place.
Electrical power calculations are needed daily by electricians, engineers, and homeowners. This calculator handles the complete power equation set including AC power factor and three-phase systems, provides NEC wire gauge recommendations, and estimates energy costs — making it a one-stop tool for electrical design and energy management. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain.
Single-phase: P = V × I × PF. Three-phase: P = √3 × V × I × PF. Apparent power: S = P / PF (VA). Reactive power: Q = S × √(1 − PF²) (VAR). Power factor: PF = P / S = cos(φ). Energy: E = P × t (in kWh). Ohm's law: R = V / I.
Result: 1,800 W (1.8 kW)
A standard 120V/15A household circuit with unity power factor delivers P = 120 × 15 × 1 = 1,800 W. At $0.12/kWh running 24 hours, that costs about $5.18/day.
Use consistent units, verify assumptions, and document conversion standards for repeatable outcomes.
Most mistakes come from mixed standards, rounding too early, or misread labels. Recheck final values before use. ## Practical Notes
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Check assumptions and units before interpreting the number. ## Practical Notes
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Apply this as a quality checkpoint for repeatable calculations.
Power factor is the ratio of real power (watts) to apparent power (VA). It ranges from 0 to 1, with 1 being ideal (resistive loads). Inductive loads like motors typically have PF of 0.8–0.9.
In AC circuits with reactive loads, current and voltage are out of phase. The apparent power (VA) accounts for this phase difference, while real power (W) is only the portion doing useful work.
In a balanced three-phase system, the line voltage is √3 times the phase voltage. The √3 factor in the power formula accounts for the combined contribution of all three phases.
Wire gauge is determined by the maximum current (ampacity) the conductor must carry. NEC tables specify ampacity ratings for each AWG size based on insulation type and installation method.
Reactive power (VAR) flows back and forth between the source and reactive loads (inductors/capacitors) without doing useful work. It is needed to maintain magnetic fields in motors and transformers.
Multiply watts by 3.412 to get BTU/hr. This is important for HVAC calculations — every watt of electrical equipment in a room eventually becomes heat that must be removed by cooling.