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Choose the direction, the type of current and the voltage. For AC circuits you can add the power factor. The result shows amps, watts, kilowatts and kilovolt-amperes (kVA).

Enter your values

Pick what you know and what you want to find.
Household sockets are single-phase AC.
Where do I find this?

Batteries, solar panels, car and USB circuits are DC.

Normal wall sockets are single-phase AC. Three-phase is used for electric stoves, wallboxes, workshops and large motors (often shown as 400 V).

230 V in most of Europe, 120 V in North America, 12 or 24 V for DC systems.
Where do I find this?

The voltage is on the device's label or in the system's description.

For three-phase use the voltage between two phases (for example 400 V), not the 230 V of a single phase.

From the device's label, in watts (1 kW = 1000 W).
Where do I find this?

The label or manual shows W or kW. Multiply kW by 1000 to get W.

Between 0.1 and 1. Use 1 for heaters and kettles, about 0.8 to 0.9 for motors if unknown.
Where do I find this?

The power factor is the share of the current that does useful work. Pure heating loads (heaters, kettles, incandescent lamps) have 1.

Motors, compressors and many power supplies are lower. If the label does not say, 0.8 to 0.9 is a common estimate. DC circuits do not need it.

Result

Enter your values to see the result.

Current
– A
Power
– kW
Apparent power
– kVA

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How it is calculated

  • DC: P = V × I
  • AC single-phase: P = V × I × power factor
  • AC three-phase: P = √3 × V × I × power factor (V between two phases)
  • Amps from watts: I = P ÷ (V × power factor) (÷ √3 more for three-phase); apparent power S = V × I

Example

A 2300 W heater on a 230 V single-phase socket with power factor 1 draws 2300 ÷ 230 = 10 A.

What this estimate leaves out

Real devices vary with load and temperature, and a starting motor draws several times its running current. Use this for planning, and ask a qualified electrician before you size cables or fuses.

Written and reviewed by QLines, Cologne · Last reviewed

FAQ

Frequently Asked Questions

How do you convert watts to amps?

Divide the power in watts by the voltage: amps = watts ÷ volts. For AC circuits also divide by the power factor, and by the square root of 3 (about 1.73) for three-phase. Example: 2300 W ÷ 230 V = 10 A.

How many amps is 1000 watts?

At 230 V, 1000 W is about 4.3 A. At 120 V it is about 8.3 A, and at 12 V it is about 83 A, because the same power needs more current at a lower voltage.

How do you convert amps to watts?

Multiply amps by volts: watts = amps × volts, and for AC also by the power factor. Example: 10 A × 230 V = 2300 W.

What is the power factor?

It is the share of the supplied current that does useful work, a number between 0 and 1. Heaters have 1, motors and many electronic devices are lower. It only matters for AC.

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