How to Figure a Horsepower Rating

James Watt defined horsepower as 33,000 pound-force-feet per minute, the amount of power that he estimated the average horse was capable of producing. The manufacturer of your vehicle probably lists its horsepower rating in its specifications, but if it does not, you can calculate it from the engine's other specs. Torque and engine speed determine horsepower. You can find your vehicle's torque from its listed specifications, and determine its engine speed from the instrument panel's rpm gauge.

Instructions

1

Find your vehicle's torque rating, measured in pound-force-feet. Your specifications may refer to this unit as "pounds-foot," "pounds-feet," "pound-feet" or simply as "pounds."

2

Multiply the torque by the engine speed, measured in revolutions per minute (rpm). For example, if your engine produces a torque of 300 pound-force-feet and rotates at 3,500 rpm: 300 x 3,500 = 1,050,000.

3

Divide your answer by 5,252. This operation combines a number of conversion steps. With this example: 1,050,000 / 5,252 = 200 horsepower.