Popular power conversions
Power units
Power is the rate at which energy is used or produced. The SI unit is the watt, one joule per second. Engines are rated in horsepower or kilowatts, and air conditioners in BTU per hour or tons of refrigeration.
| Unit | Symbol | In watts | Definition |
|---|---|---|---|
| Milliwatt | mW | 0.001 W | |
| Watt | W | 1 W | The SI unit of power: one joule per second. |
| Kilowatt | kW | 1,000 W | One thousand watts, about 1.341 mechanical horsepower. |
| Megawatt | MW | 1,000,000 W | |
| Gigawatt | GW | 1,000,000,000 W | |
| Horsepower | hp | 745.6998716 W | Mechanical (imperial) horsepower: 550 foot-pounds per second, about 745.7 watts. |
| Metric horsepower | PS | 735.49875 W | Exactly 735.49875 watts, used for car engines in Europe and Asia. |
| BTU per hour | BTU/h | 0.2930710702 W | |
| Ton of refrigeration | TR | 3,516.852842 W | 12,000 BTU per hour, about 3.517 kilowatts; used to size air conditioners. |
Calculate with power
The smart calculator does arithmetic across power units and picks a sensible unit for the answer. Try 150 hp to kW.
Questions and answers
Which power units can I convert?
All 9: milliwatts, watts, kilowatts, megawatts, gigawatts, horsepower, metric horsepower, BTU per hour, tons of refrigeration.
What is the SI unit of power?
This converter uses the watt (W) as its base unit. Power is the rate at which energy is used or produced. The SI unit is the watt, one joule per second. Engines are rated in horsepower or kilowatts, and air conditioners in BTU per hour or tons of refrigeration.
What is the difference between hp and PS?
Mechanical horsepower (hp) is about 745.7 W. Metric horsepower (PS, CV) is 735.5 W, about 1.4% less.
How precise are the results?
Factors are the exact legal definitions where one exists (an inch is exactly 2.54 cm, a pound exactly 0.45359237 kg). Results show 10 significant digits by default; the precision menu offers 4 to 15.
Does the power converter work offline?
Yes. ConvertEasy is a progressive web app: after your first visit it keeps working with no connection, and you can install it to your home screen from the browser menu.