AC Wattage Calculator

AC stands for Alternating Current — an electric current that periodically reverses direction, unlike DC (Direct Current) which flows in one direction only. AC is the standard form of electricity delivered to homes and businesses by power grids worldwide. It powers everything from household appliances and lighting to industrial motors and HVAC systems.

Wattage is a measure of the amount of real power consumed or produced by an electrical device, expressed in watts (W). It tells you how much energy per second a device uses. For homeowners, wattage determines electricity bills; for engineers, it's essential for sizing circuits, generators, and protection devices.

To calculate AC wattage you need three values: voltage (V) in volts, current (I) in amperes, and the power factor (PF) — a dimensionless number between 0 and 1. You also need to know whether your circuit is single-phase or three-phase, as the formulas differ. This calculator handles all these cases automatically.

For single-phase AC circuits, real power is calculated using the formula P = PF × I × V. For example, a circuit with a power factor of 0.8, 10 A of current, and 120 V gives P = 0.8 × 10 × 120 = 960 W. Simply multiply the voltage, current, and power factor together.

For three-phase line-to-line voltage, the formula is P = √3 × PF × I × V. For line-to-neutral voltage, it becomes P = 3 × PF × I × V. The √3 (approximately 1.732) factor accounts for the phase relationships between the three conductors. This calculator automatically applies the correct formula based on your selected configuration.

Real power (W) is the actual power consumed to do useful work. Apparent power (VA) is the total power supplied by the source, combining both real and reactive components. Reactive power (VAR) is the power stored and released by inductive or capacitive elements — it does no useful work but is required to maintain voltage levels. The relationship is: Apparent Power² = Real Power² + Reactive Power².

Power factor (PF) is the ratio of real power to apparent power, ranging from 0 to 1. A PF of 1 means all supplied power is used effectively. Resistive loads like heaters have a PF close to 1, while inductive loads like electric motors typically have a PF around 0.8. Utilities prefer customers to maintain a high power factor to reduce transmission losses.

This calculator is designed to calculate wattage from voltage, current, and power factor. To find current from known wattage, rearrange the single-phase formula: I = P / (PF × V). For three-phase line-to-line, use I = P / (√3 × PF × V). You can perform these rearrangements manually using the formulas provided.