The horsepower (hp) is a unit in the foot-pound-second ( fps ) or English system, sometimes used to express the rate at which mechanical energy is expended. It was originally defined as 550 foot-pounds per second (ft-lb/s). A power level of 1 hp is approximately equivalent to 746 watt s (W) or 0.746 kilowatt s (kW). To convert from horsepower to watts, multiply by 746. To convert from watts to horsepower, multiply by 0.00134. To convert from horsepower to kilowatts, multiply by 0.746.