This Video Explains the Difference Between Horsepower and Torque in Under 4 Minutes
The automotive YouTube channel Engineering Explained details the differences and overlaps between horsepower and torque.
Car enthusiasts know these two words mean a lot with respect to a car -- torque and horsepower. Given how frequently they pop up in automobile advertisements, trade shows, and in general car discussion, it's easy to forget that these two measurements aren't actually interchangeable. They're closely related but they involve two very distinct aspects of work.
So what exactly is the difference and how do these two units involve one another? That's where this simple, 4-minute explanation from the car fans over at Engineering Explained come into play. Despite the fact that this video is over 6 years old, the video holds up really well.
In short, horsepower involves the power produced by an engine. Technically, a horsepower is the power needed to move 33,000 pounds (14,968 kg) one foot (30.48 cm) in one minute. (And power, given the basic physics definition, is just the rate of work.)
Horsepower is measured through a dynamometer which places a load on the engine and then measures the force the engine's crankshaft puts against the load (and that load is normally a break).
This is where the two terms start overlapping. The dynamometer measures torque output of the engine. Torque is taken at several RPMs. Those numbers get put into the formula of Torque X RPM / 5,252. The resulting number is the horsepower. Just in case you needed a visual aid or two with this explanation, don't worry. The video will tack on plenty of hand-drawn graphs and the equations completely written out. And, if you really need a "real-world" example outside of automobiles, finish out the video to hear a good comparison to torque, horsepower, and bodybuilding.