How to Calculate Watts

Volts times amps

Watts are volts times amps. A 120 volt circuit drawing 10 amps uses 1,200 watts, which is 1.2 kilowatts.

With ohms, square the volts and divide by the ohms, or square the amps and multiply by the ohms. This page only does that multiplication. It does not size a breaker or a wire.

Questions

How do you calculate watts?

Multiply volts by amps. 120 volts times 10 amps is 1,200 watts.

How do you calculate watts from ohms?

If you know volts and ohms, divide volts squared by ohms. If you know amps and ohms, multiply amps squared by ohms.

How many watts are in a kilowatt?

1,000 watts is 1 kilowatt. 1,200 watts is 1.2 kilowatts.