Horsepower (hp) is a unit of measurement that expresses the rate at which work is done.
1 hp represents the amount of power it takes to perform 33,000 ft.-lbs. of work in 1 minute.
Imagine a horse pulling coal out of a mine. A horse exerting 1 horsepower can raise:
- 330 lbs. of coal 100 ft. in 1 minute.
-OR-
- 33 lbs. of coal 1,000 ft. in 1 minute.
- Etc.
How is it measured?
- Engine specs will list peak horsepower at a specific rpm.
- A dynamometer (dyno) measures torque and uses it to calculate horsepower.
- The formula to calculate horsepower is:
(rpm x Torque) ÷ 5,252 = Horsepower
For example, if an engine makes 325 lb-ft at 3,880 rpm, it would be:
(3,880 x 325) ÷ 5,252 = 240 hp
Notes
- The difference between Torque and horsepower is:
-
- Torque explains how MUCH has been accomplished.
- Horsepower explains how FAST it's done.
- Australia and other countries that use the metric system measure horsepower in Watts or Kilowatts.