# Pound-foot (torque)

A pound-foot (lbf⋅ft) is a unit of torque (a pseudovector). One pound-foot is the torque created by one pound of force acting at a perpendicular distance of one foot from a pivot point. Conversely one pound-foot is the moment about an axis that applies one pound-force at a radius of one foot.

Pound-foot
Unit systemBritish Gravitational System, English Engineering Units
Unit ofTorque
Symbollbf∙ft
Conversions
1 lbf∙ft in ...... is equal to ...
SI units   ≈ 1.355818 N⋅m
Gravitational metric system   ≈ 0.1382550 kgf⋅m

The value in SI units is given by multiplying the following approximate factors:

One pound (force) = 4.448 222 newtons
One foot = 0.3048 m

This gives the conversion factor:

One pound-foot = 1.35582 newton metres.

The name "pound-foot", intended to minimize confusion with the foot-pound as a unit of work, was apparently first proposed by British physicist Arthur Mason Worthington. However, the torque unit is often still referred to as the foot-pound (ft⋅lbf).

Similarly, an inch-pound (though should be more correctly as pound-inch) is the torque of one pound of force applied to one inch of distance from the pivot, and is equal to 1/12 of a pound-foot. It is commonly used on torque wrenches and torque screwdrivers for setting specific fastener tension.