Pound-force
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The pound-force is a non-SI unit of force or weight (properly abbreviated "lbf" or "lbf"). The pound-force is equal to a mass of one avoirdupois pound (which is currently defined as exactly 0.45359237 kilogram) multiplied by the standard acceleration due to gravity on Earth. (The pound-force is thus roughly the force exerted due to gravity by a mass of one pound at the surface of the Earth.)
Though pounds-force had been used in low-precision measurements since the 18th century, they were never well-defined units until the 20th century. It was in 1901 when the CGPM first adopted a standard acceleration of gravity for the purpose of defining grams-force and kilograms-force, a value often borrowed to define pounds-force, though other values such as 32.16 ft/s² (9.80237 m/s²) have been used as well. If the metric value of exactly 9.80665 m/s², or approximately 32.174 05 ft/s², is used this gives a force of 4.448222 newtons for one pound-force.
See also
- pound (weight) for a more complete discussion of customary units of force and mass.
- pound-force per square inch for a unit of pressure
- foot-pound force, a unit of work, energy, or torque
| Newton (SI unit) | Dyne | Kilogram-force (Kilopond) | Pound-force | Poundal | |
| 1 N | = 1 kg·m/s² | = 105 dyn | ≈ 0.10197 kp | ≈ 0.22481 lbf | ≈ 7.2330 pdl |
| 1 dyn | = 10−5 N | = 1 g·cm/s² | f | ||
| 1 kp | = 9.80665 N | = 980665 dyn | Acceleration due to gravity>gn·(1 kg) | ≈ 2.2046 lbf | ≈ 70.932 pdl |
| 1 lbf | ≈ 4.448222 N | ≈ 444822 dyn | ≈ 0.45359 kp | gn·(1 Pound (mass)>lb) | ≈ 32.174 pdl |
| 1 pdl | ≈ 0.138255 N | ≈ 13825 dyn | ≈ 0.014098 kp | ≈ 0.031081 lbf | ft/s² |
| The value of gn as used in the official definition of the kilogram-force is used here for all gravitational units. | |||||
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