How to Calculate the Average Horsepower
- 1). Multiply the torque generated by the engine, as expressed in units of foot-pounds (ft-lb), by the rpm of the engine while providing this torque. You can obtain a torque and rpm measurement for your engine by taking your vehicle to a professional experienced with using a dynamometer, which he will attach to your engine's crankshaft.
- 2). Divide the product obtained in Step 1 by 5,252. (James Watt came up with the horsepower unit, and defined one horsepower to be 1 ft-lb of torque at 5,252 rpm, which is also equal to 33,000 ft-lb per minute of work.)
- 3). The result of your division in Step 2 is the calculated horsepower. For example, if an engine was producing 250 ft-lb of torque at 5,000 rpm, the equation for calculating horsepower would be:
Horsepower = [(250) x (5,000)] / 5,252 = 238
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