Watts to amps calculator

What is a watts to amps calculator?

A watts to amps calculator converts electrical power, measured in watts, into electric current, measured in amps, once you know the voltage of the circuit. Power tells you how much energy a device uses every second, while current tells you how much charge flows through the wires. Knowing the current draw is useful for choosing the right fuse or breaker, sizing wires, and making sure a circuit is not overloaded.

Formula

Current is power divided by voltage:

where $I$ is the current in amps (A), $P$ is the power in watts (W), and $V$ is the voltage in volts (V). The voltage must be greater than zero, since dividing by zero is undefined.

How to use

1. Enter the power of the device in watts.
2. Enter the supply voltage in volts.
3. The calculator instantly shows the current in amps. The result appears only when both values are present and the voltage is not zero.

Worked example

Suppose a heater is rated at 600 watts and runs on a 120-volt supply. The current it draws is:

So the heater pulls 5 amps, which means a standard 15-amp household circuit can comfortably power it.

FAQ

Does this formula work for both AC and DC?

It works directly for DC circuits and for purely resistive AC loads. For reactive AC loads (motors, transformers) you also need the power factor, where amps = watts ÷ (volts × power factor).

Why does the result disappear when I enter 0 volts?

Dividing power by zero voltage has no meaningful answer, so the calculator hides the result until you enter a voltage greater than zero.