|Unit system||British Gravitational System, English Engineering Units|
|1 lbf⋅ft in ...||... is equal to ...|
|SI units||≈ 1.355818 N⋅m|
|Gravitational metric system||≈ 0.1382550 kgf⋅m|
A pound-foot (lb⋅ft), abbreviated from pound-force foot (lbf · ft), is a unit of torque representing one pound of force acting at a perpendicular distance of one foot from a pivot point. Conversely one foot pound-force (ft · lbf) is the moment about an axis that applies one pound-force at a radius of one foot.
The value in SI units is given by multiplying the following exact factors:
This gives the exact conversion factor:
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.
Despite this, in practice torque units are commonly called the foot-pound (denoted as either lb-ft or ft-lb) or the inch-pound (denoted as in-lb). Practitioners depend on context and the hyphenated abbreviations to know that these refer to neither energy nor moment of mass (as the symbol ft-lb rather than lbf-ft would imply).
Similarly, an inch-pound (or 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 lbf⋅ft (0.1129848 N⋅m). It is commonly used on torque wrenches and torque screwdrivers for setting specific fastener tension.