Power Calculator
Watts, kilowatts and horsepower, with a running cost.
Work out Power. Watts, kilowatts and horsepower, with a running cost. Shows the working, not just the answer.
Optional — for the running cost.
Power (watts)
1,000
1 kW · 1.341 hp
Power is energy divided by time — the rate of doing work, not an amount of it. One horsepower is 745.7 W, defined from 550 foot-pounds per second, which James Watt estimated as what a dray horse could sustain. A kilowatt-hour, the unit on an electricity bill, is 3.6 million joules.
How the Power Calculator works
Power is energy divided by time — a rate, not an amount. One horsepower is 745.7 watts, defined from 550 foot-pounds per second, which James Watt estimated as what a dray horse could sustain. A kilowatt-hour is 3.6 million joules.
Also known as: watts calculator · horsepower calculator · power formula physics · how to calculate power
Frequently asked questions
How do I calculate power?
Divide energy by time. 3.6 million joules over an hour is 1,000 watts, or 1 kW.
How many watts is one horsepower?
745.7 for mechanical horsepower. Metric horsepower is slightly different at 735.5, which is a common source of small discrepancies in specifications.
What is a kilowatt-hour?
The energy used by a 1 kW device running for an hour — 3.6 million joules. It is the unit an electricity meter counts, which is why this page can convert power into a running cost.
What is the difference between power and energy?
Energy is the quantity; power is the rate. A bill charges for kilowatt-hours of energy, while the appliance is rated in watts of power.
Put this calculator on your own site
Free to use, on any site, commercial or not. Paste this where you want it to appear. It is a plain iframe, so it works in WordPress, Squarespace, Wix, Webflow, Ghost and anything else that accepts HTML.
<iframe src="https://www.thecalclibrary.com/embed/power-calculator" width="100%" height="640" style="border:1px solid #e2e8f0;border-radius:12px" loading="lazy" title="Power Calculator"></iframe>The only condition is that the credit line stays visible. It sits inside the frame, so you do not have to do anything to keep it.
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