Power Converter
Power converter for watts, kilowatts, BTU per hour and all three horsepower definitions, plus a plain explanation of why kW and kWh aren't the same thing.
Most used power tools
Watts to Horsepower
Mechanical, metric and electrical horsepower kept separate, since they differ by up to 1.4 percent.
Watts to Amps
Current draw for a given power, with power factor.
Electrical Converter
Watts, volts, amps and ohms from any two.
Convert every unit at once
Enter a number.
Reference only. Motor sizing, circuit protection and conductor selection must follow the electrical code that applies where you are, and should be verified by a qualified electrician.
Every power converter on this site
Reference table
| Unit | In watts | Exact? |
|---|---|---|
| 1 kilowatt | 1,000 W | Exact |
| 1 megawatt | 1,000,000 W | Exact |
| 1 mechanical hp | 745.699872 W | 550 ft-lbf/s, rounded here |
| 1 metric hp (PS) | 735.49875 W | Exact, 75 kgf-m/s |
| 1 electrical hp | 746 W | Exact, IEEE and NEMA |
| 1 BTU (International Table) per hour | 0.29307107 W | Rounded |
Power isn't energy
Power is the rate at which energy is used, so a watt is one joule per second. A 100 watt bulb left on for an hour consumes 100 watt-hours of energy, and those are different quantities with different units.
Confusing kW with kWh on an electricity bill is the everyday version of this. kW is how fast you are using power; kWh is how much you used. The energy converter handles the second.
Three horsepowers, and BTU per hour
Horsepower has never had one definition, and this tool carries both common ones. The dedicated page covers the 1.4 percent gap between mechanical hp and metric PS, and why electrical horsepower is exactly 746 watts.
BTU per hour appears mainly on heating and air conditioning equipment in North America. A 12,000 BTU/h unit, often sold as one ton of cooling, is about 3,517 watts.
Common questions
How many watts is 1 kW?
Exactly 1,000 watts. Kilo is an SI prefix meaning exactly one thousand, so unlike the kilobyte there is no second convention here and no ambiguity to resolve.
What is the difference between kW and kWh?
kW is power, the rate of energy use. kWh is energy, the amount used over time. A 2 kW heater running for three hours uses 6 kWh.
How many watts is 1 hp?
About 745.7 for mechanical horsepower (550 ft-lbf/s), exactly 735.49875 for metric horsepower or PS (75 kgf-m/s), and exactly 746 for electrical horsepower as set by IEEE and NEMA.
What is 12,000 BTU per hour in watts?
About 3,517 watts. That rating is common on air conditioners and is often described as one ton of cooling.
Sources
- NIST Guide to the SI, Appendix B: Conversion Factors. National Institute of Standards and Technology. Source for every conversion factor on this page, and for which factors are exact rather than rounded.