kW to hp converter

Three kinds of horsepower

Mechanical horsepower, used in the US and UK, is 550 foot-pounds per second, which works out at 745.69987158 watts. Metric horsepower, written PS in Germany and CV in France and Italy, is 75 kilogram-force metres per second: exactly 735.49875 watts. Electrical horsepower, used for motors, is exactly 746 watts. Source: NIST Special Publication 811, Appendix B. The main answer is in mechanical horsepower, with the other two beside it.

Worked example

100 kW is 100,000 W. 100,000 ÷ 745.69987 = 134.1 hp, or 100,000 ÷ 735.49875 = 136.0 PS. Going back, 150 hp × 0.74569987 = 111.9 kW.

Car figures in Australia

Australian and European car makers give engine power in kilowatts. American and British reviews often quote horsepower, and European brochures often quote PS. Metric horsepower is about 1.4% smaller than mechanical horsepower, so the same engine is "136 PS" in Germany and "134 hp" in the US. Check which one a figure uses before comparing cars.

A quick check in your head

Multiply kilowatts by 4 and divide by 3 for horsepower: 150 kW gives about 200 hp (exactly 201.2). For horsepower to kilowatts, multiply by 3 and divide by 4. For watts, kilowatt-hours and other power and energy units, use the unit converter.

Rounding

The answer is worked out from the exact definition, then shown to 4 decimal places (6 significant figures for numbers below 1). It says "exactly" only when nothing was rounded.