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A pound-foot ( lb⋅ft), abbreviated from pound-force foot ( lbf · ft), is a unit of torque representing one pound-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.
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). In most US industrial settings, the torque ranges are given in ft-lb rather than lbf-ft. (2010). 9781435439337, Cengage Learning. ISBN 9781435439337 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 . It is commonly used on and torque screwdrivers for setting specific fastener tension. An inch-ounce is a smaller unit, equal to of an inch-pound.
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