First, that power must be calculated by multiplying together the average pressure on the pistons, the area of each piston, the length of the piston's stroke, the number of power strokes per minute per piston, and the number of pistons in the engine. The indicated horsepower is determined by dividing the power by 33,000 foot-pounds per minute. Brake horsepower is sometimes called effective horsepower because it is the amount of power available at the engine's output shaft. Brake horsepower is determined by the engine's speed and torque, the amount of twist exerted. A machine called a dynamometer measures brake horsepower.
Brake horsepower is the rating most widely used by engineers.
It is less than indicated horsepower due to friction and other power losses in the engine. S.A.E. horsepower defines the power of an engine under specified conditions and allows valid comparisons between engines. It is used in determining licensing fees for automobiles in some states. How to cite this article.