Amps to watts calculator

What is an amps to watts calculator?

An amps to watts calculator turns a measured current and voltage into electrical power. Current is measured in amperes (amps, A), voltage in volts (V), and the result, power, in watts (W). This conversion is handy when sizing wiring, picking a power supply, or working out how much energy a device draws from a circuit.

Formula

Power equals current multiplied by voltage:

where $P$ is power in watts, $I$ is current in amps, and $V$ is voltage in volts. This is the direct-current (DC) form; for purely resistive loads it also holds for alternating current.

How to use

1. Enter the current in amps.
2. Enter the voltage in volts.
3. Read the resulting power in watts. The result appears only once both fields are filled in.

Worked example

Suppose a device draws 5 A on a 120 V supply:

So the device consumes 600 watts of power.

FAQ

Does this work for alternating current (AC)?

For a purely resistive load (like a heater or incandescent bulb), watts = amps times volts works directly. For reactive loads (motors, transformers), real power also depends on the power factor, so multiply by that factor for an accurate figure.

How do I go the other way, from watts to amps?

Divide power by voltage: amps = watts / volts. Use the watts to amps calculator for that conversion, or the Ohm’s law calculator to relate voltage, current, and resistance.