# Foot-pound (energy)

The **foot pound-force** (symbol: **ft⋅lbf** or **ft⋅lb**)[1] is a unit of work or energy in the Engineering and Gravitational Systems in United States customary and imperial units of measure. It is the energy transferred upon applying a force of one pound-force (lbf) through a linear displacement of one foot. The corresponding SI unit is the joule.

Foot-pound | |
---|---|

Unit system | English Engineering units and British Gravitational System |

Unit of | Energy |

Symbol | ft⋅lbf |

Conversions | |

1 ft⋅lbf in ... | ... is equal to ... |

SI units | 1.355818 J |

CGS units | 13,558,180 erg |

## Usage

The foot-pound is often used to specify the muzzle energy of a bullet in small arms ballistics, particularly in the United States.

"Foot-pound" is also used as a unit of torque (see *pound-foot (torque)*). In the United States this unit is often used to specify, for example, the tightness of a bolt or the output of an engine. Although they are dimensionally equivalent, energy (a scalar) and torque (a Euclidean vector) are distinct physical quantities. Both energy and torque can be expressed as a product of a force vector with a displacement vector (hence pounds and feet); energy is the scalar product of the two, and torque is the vector product.

## Conversion factors

### Energy

1 foot pound-force is equivalent to:

### Power

1 foot pound-force per second is equivalent to:

- 1.355817948 watts
- 1.818×10
^{−3}horsepower

Related conversions:

- 1 watt ≈ 44.25372896 ft⋅lbf/min = 0.737562149333 ft⋅lbf/s
- 1 horsepower (mechanical) = 33,000 ft⋅lbf/min = 550 ft⋅lbf/s

## References

- Budynas, Richard G.; Nisbett, J. Keith (2014-01-27).
*Mechanical Engineering Design*. McGraw Hill Education. ISBN 978-0073529288.