In physics, a foot-pound (symbol ft·lbf or ft·lbf) is an Imperial and U.S. customary unit of mechanical work, or energy, although in scientific fields one commonly uses the equivalent metric unit of the joule (J). There are approximately 1.356 J/(ft·lbf).
To calculate a foot-pound, you can use this formula,
- W = F × D
where W is work (in foot-pounds), F is force (in pounds), and D is distance (in feet) over which the force is applied (measured in the direction of the force).
The foot-pound is also the unit of torque, which is conventionally expressed in SI units as newton-meters rather than joules. Sometimes the order of the units is reversed for torque, expressed as pound-feet rather than foot pounds.
Doing 550 foot-pounds of work on an object in one second is equal to a horsepower, an Imperial and U.S. customary unit of power.