Convert amps to watts for DC, single-phase AC and three-phase circuits. Enter the current, the voltage and, for AC, the power factor. Free, private, and runs entirely in your browser.
Power is current multiplied by voltage. In AC circuits the power factor scales the real power, and three-phase systems add a factor of the square root of 3 for line-to-line voltage.
How many watts is 10 amps? At 120 V it is 1,200 W, and at 240 V it is 2,400 W for a purely resistive load.
How do I get kilowatts? Divide watts by 1,000. The result shows kilowatts as well.
A circuit carries 10 A at 120 V DC: P = 10 × 120 = 1,200 W. As single-phase AC with a power factor of 0.8, P = 10 × 120 × 0.8 = 960 W. A three-phase load of 20 A at 400 V and a power factor of 0.9 gives 1.732 × 20 × 400 × 0.9 ≈ 12,471 W.
Can I convert amps to watts without voltage? No. You need the voltage, since power is current times voltage.
Does the result include losses? No. It is the power at the load for the values you enter, not wiring or conversion losses.
The watt is named for James Watt, the Scottish engineer whose steam engine improvements made power a practical concept, and the ampere honors the French physicist André-Marie Ampère, a founder of electrodynamics in the 1820s. International electrical congresses fixed the units in the late 19th century, which is why P = V × I works the same worldwide. Three-phase power spread in the 1890s because it delivers power more smoothly and needs less copper per kilowatt.
Use this calculator to turn a current rating into power, for example to see how much a 20 A, 240 V circuit can supply: 4,800 W. It also helps compare equipment rated in amps with equipment rated in watts or kilowatts, and to estimate running cost once you know the hours of use.
Why is real power lower than volt-amps in AC? Reactive loads such as motors store and return energy, so some current does no useful work. The power factor measures how much does.
What is a typical household voltage? About 120 V in North America and 230 V in much of the rest of the world.