Calculate power from force, distance and time, and convert between watts, kilowatts and the different horsepower units.
Power = force × distance ÷ time. One mechanical horsepower is 550 foot-pounds per second, which equals 745.7 watts. To convert, multiply horsepower by 0.7457 to get kilowatts.
Horsepower is a unit of power — the rate at which work is done. This calculator finds power from first principles (force × distance ÷ time) and shows the answer in watts, kilowatts, three kinds of horsepower and BTU per hour. A second tool converts directly between those units.
It is handy for comparing engines and motors, sizing pumps and compressors, and checking spec sheets that mix hp, PS and kW. To estimate a car's engine power from a quarter-mile run, use the Engine Horsepower Calculator.
Everything is converted to SI units first, and the result is expressed in the unit you need.
| Calculation | Result |
|---|---|
| 550 lbf pushing 1 foot (0.3048 m) in 1 second | 1 hp |
| 1,000 N over 10 m in 2 s (5 kW) | 6.70511 hp |
| 100 mechanical hp in kW | 74.56998716 kW (kW) |
| 1 kW in mechanical hp | 1.34102209 hp |
| 150 PS (metric hp) in mechanical hp | 147.94801059 hp |
| Unit | Definition | Watts |
|---|---|---|
| Mechanical horsepower (hp) | 550 foot-pounds per second | 745.7 W |
| Metric horsepower (PS, CV, hp(M)) | 75 kgf·m per second | 735.5 W |
| Electrical horsepower | Defined as exactly 746 W | 746 W |
| Boiler horsepower | 34.5 lb of water evaporated per hour at 212 °F | 9,809.5 W |
| Kilowatt (kW) | SI unit — 1,000 joules per second | 1,000 W |
The word “horsepower” means different things. Mechanical horsepower (hp) is used in the US and UK. Metric horsepower is labelled PS, CV or hp(M) on European and Asian car specifications — it is about 1.4% smaller. Electrical horsepower is simply 746 W and is used for motors. Always check which one a spec sheet means.
Horsepower is a unit of power — how fast work is done. One mechanical horsepower equals 550 foot-pounds of work per second, or about 745.7 watts.
Multiply force by distance and divide by time to get power in watts, then divide by 745.7 for mechanical horsepower.
1 mechanical hp is 745.7 W, 1 metric hp (PS) is 735.5 W, and 1 electrical hp is 746 W.
Multiply horsepower by 0.7457. For example, 100 hp is 74.57 kW. To go the other way, multiply kW by 1.341.
Metric horsepower (PS) is slightly smaller: 1 hp = 1.01387 PS, so a 150 PS engine is about 148 hp.
A unit for steam boilers: the heat needed to evaporate 34.5 lb of water per hour at 212 °F, about 9.81 kW.
SI uses the watt for power. Horsepower survives for engines and motors from the days of James Watt, who defined it to compare steam engines with horses.
Engine horsepower is measured on an engine or chassis dynamometer, or estimated from a vehicle's acceleration. Use the Engine Horsepower Calculator for that.
A unit of heat flow used in heating and cooling. One watt equals about 3.412 BTU/h, and one horsepower is about 2,544 BTU/h.
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