Horsepower (hp) is an imperial unit of power equal to approximately 745.7 watts, originally defined by James Watt to compare steam engine output to draft horses. It remains the standard unit for rating car engines, lawnmowers, and boat motors, especially in the United States. One horsepower equals about 0.7457 kilowatts or 1.0139 metric horsepower.

Foot-pounds per second (ft·lbf/s) equals approximately 1.356 watts, an imperial power unit occasionally used in mechanical engineering contexts. While less common than horsepower for engine ratings, it provides a direct connection between torque and rotational speed. One foot-pound per second equals about 1.356 watts or 0.00182 horsepower.