Electrical Power Calculator

Calculate watts, kilowatt hours and running cost from voltage, current and hours of use.

Quick answer: Electrical Power Calculator: Calculate watts, kilowatt hours and running cost from voltage, current and hours of use. Everything runs in your browser, so nothing you enter is uploaded or stored.

Voltage (V)

Current (A)

Hours used per day

Price per kWh

How to use Electrical Power Calculator

Enter your values in the fields.
The results update instantly as you type.
Note or copy the numbers you need.

Features

Instant results
Free, no signup
Runs in your browser, nothing is uploaded
Works on phone and desktop

Formula

Watts = volts x amps. kWh = watts / 1000 x hours.

Worked example

A 120 V, 5 A device uses 600 W. Four hours a day is 2.4 kWh, costing about 0.38 a day at 0.16 per kWh.

Frequently asked questions

How do I calculate watts?

Watts = volts x amps.

How do I calculate running cost?

kWh = kW x hours, then multiply by your electricity price.

Is the Electrical Power Calculator free?

Yes. It is free, needs no signup and works on any device.