Ask the Editors: What In The World Is a Foot-Pound?

It gets a little complicated, but it is all connected.

Not a stupid question at all. Horsepower, though really fairly inaccurate if taken at literal value, at least makes sense: How many horses would it take to make this type of power output.

A foot-pound, by comparison, sounds like some kind of dance move. It too is simpler than you think, though. It is a measurement of how much effort it would take to lift a one pound weight one foot off the ground.

We use this measurement here in the United States but the rest of the world (International System of Units (SI)) calls this measurement a joule.

If you want to be technical, though, one foot-pound is not exactly one joule but rather 1.3558179483314004 joules.

This can all be rather confusing, for sure, so let’s add a bit more confusion to the equation. The foot-pound does indeed have a connection to horsepower. We got the term horsepower from James Watt (yes the same Scottish inventor who the unit of electrical power is named after). He also happened to invent the idea of horsepower as a unit of measurement.

He determined that a single horse could lift 550-pounds one foot off the ground at a rate of 1 second and called that a horsepower.

So to convert horsies to foot pounds, divide the number of horsepower by 0.00181818 to get your foot-pounds (per second).

Ready for where it really gets wild? There is also the pound-foot and it isn’t the same thing!

The pound-foot is an English unit of torque as well but it deals mostly with angular requirement of linear force. What in the world does that mean, you wonder? Think about how much torque it would take for your wrench to loosen a nut at the end of a bolt.

The SI equivalent of the pound-foot is not the joule, of course, but rather the Newton meter (Nm).

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