Watts/Amps/Volts Converter

Convert between watts, amps, and volts for single-phase and three-phase electrical circuits.

Results

Visualization

How It Works

Watts, amps, and volts are the three pillars of electrical measurement. Watts measure real power consumed, amps measure current flow, and volts measure electrical pressure. Power factor accounts for inefficiency in AC circuits with motors or transformers.

The Formula

Single Phase: W = V x A x PF  |  Three Phase: W = V x A x PF x √3

Variables

  • W — Real power in watts -- the actual energy consumed
  • V — Voltage in volts -- the electrical pressure
  • A — Current in amperes -- the flow of electricity
  • PF — Power factor (0 to 1) -- ratio of real power to apparent power
  • VA — Apparent power in volt-amperes -- total power drawn from the source

Example

A 1,800W space heater on a 120V single-phase circuit with PF=1.0 draws: 1800 / (120 x 1.0) = 15 amps. It needs a 20A circuit (15A x 1.25 continuous load rule).

Tips

  • Resistive loads like heaters and incandescent lights have a power factor of 1.0.
  • Motors typically have a power factor of 0.8 to 0.9 -- they draw more amps than you might expect.
  • The NEC requires circuits to be loaded to no more than 80% of their rating for continuous loads.
  • Three-phase power delivers 1.732 times more power than single-phase at the same voltage and current.
  • When in doubt about power factor, use 0.85 as a safe conservative estimate for mixed loads.