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The foot-pound force, or simply foot-pound (symbol: ft-lbf or ft-lb) is a unit of work or energy in the English Engineering Units and Gravitational Systems in United States customary and Imperial units of measure. It is the energy transferred on applying a force of 1 pound-force (lbf) through a displacement of 1 foot (ft). The corresponding SI unit is the Joule.


The foot-pound is an obsolete term used particularly in the United States. The foot-pound is often used to specify the muzzle energy of a bullet in small arm ballistics, the tightness of a bolt and the output of an internal combustion engine.

The foot-pound can be expressed either as energy or torque. Although they are dimensionally equivalent, energy (a scalar), and torque (a vector) are distinct physical quantities.


When the foot-pound is expressed as an integral of force and displacement it arises from a dot product. Muzzle energy and the chemical energy released by liquid fuel in an internal combustion engine are examples of the dot product.


The "Foot-pound" is also the name of a unit of torque (see Pound-foot (torque)). Torque is product of a force vector with a displacement vector and is a cross product. The measurement of a torque wrench or engine torque are examples of the cross product.

Conversion to other units

Energy units

1 foot-pound is equivalent to:

  • 1.3558179483314 joules
  • 13,558,179.483314 ergs
  • 0.001285067 British Thermal Units
  • 0.323832 gram calories
  • 0.000323832 kilogram calories or food calories

Power units

  • 1 watt 44.25372896 ft-lbf/min
  • 1 horsepower (mechanical) = 33,000 ft-lbf/min = 550 ft-lbf/s

See also

External links

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