Watts to Amps: Current from Power and Voltage

The current a load draws is its power divided by the voltage that delivers it: I = P / V for DC, I = P / (V × PF) for single-phase AC and I = P / (sqrt(3) × V × PF) for balanced three-phase, where V is the line-to-line voltage and PF is the power factor. Change the watts, the supply voltage, the supply type and the power factor, and watch the ammeter, the charge dots in the wires and the comparison bars respond.

Current drawn I

4.348 A

I = 1000 / (230 × 1.00) = 4.348 A

Apparent power S 1000 VA

Load resistance R 52.90 Ω

Supply typeSingle-phase AC

Load power P1000 W

Supply voltage V230 V

Power factor PF1.00

Nominal supplies: 230 V (UK/Europe), 120 V (North America), 400 V and 480 V three-phase. P is the electrical input power in watts. This is physics, not an installation guide: cable sizing and circuit protection follow local wiring regulations and a qualified electrician.

Single-phase AC: V is the rms supply voltage. A power factor below 1 means more current for the same watts.

reactive power Q = 0 var

S = P / PF is the apparent power the supply has to carry, in VA · R = V² / P = V / I for a resistive load (DC, or AC at PF 1)

Tip: a 2000 W load draws 8.696 A at 230 V but 16.67 A at 120 V (two appliances, each rated 2000 W for its own supply; a 230 V kettle moved to 120 V would draw far less). Put 10000 W on 400 V at PF 0.85 and switch from single-phase to three-phase: the current in each line falls by sqrt(3), from 29.41 A to 16.98 A.