Power Unit Converter (W, kW, PS, HP)

Converts power into watts, kilowatts, megawatts, metric horsepower (PS), mechanical horsepower (HP) and kilocalories per hour. Japanese car specifications use PS, which is 735.49875 W, and that is not the same as HP.

Explanation

Enter a power and choose its unit, and every other unit follows. Horsepower converts to kilowatts exactly as easily as kilowatts convert back.

Two kinds of horsepower

There are two horsepowers, and they are not equal.

1 PS (metric horsepower) = 735.49875 W — lifting 75 kgf by one metre in one second
1 HP (mechanical horsepower) = 745.6999 W — lifting 550 lbf by one foot in one second

Japanese and European car specifications quote PS; American ones quote HP. The same "200 horsepower" therefore differs by about 1.4% depending on which side of the ocean printed it.

Example

Convert 100 PS.

100 \times 735.49875 = 73549.875\ \text{W} = 73.55\ \text{kW}

In mechanical horsepower that is 98.63 HP. The engine did not shrink; the same output is simply being measured with a different ruler.

Where it is used

Car engines: a Japanese kei car is capped at 64 PS, about 47 kW
Appliances are rated in watts, power stations in megawatts
The unit exists because James Watt sold steam engines by comparing them to the horses they replaced

Watch out

The SI unit is the watt. Horsepower survives by custom only, and Japanese weights-and-measures law does not permit it for trade or certification.