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This editable Main Article is under development and subject to a disclaimer.

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## Contents

* 1 Definition in terms of the SI unit of force
* 2 Equivalent units of force
* 3 Notes
* 4 References

The pound-force (symbol: lbf [note 1] ) is a measurement unit of force which will accelerate 1 pound of mass to 9.80665 m/s2 (≈ 32.17405 ft/s2), the standard average acceleration due to gravity on Earth's surface (referred to as gn [1]). It is used primarily in the United States and is equivalent to exactly 4.4482216152605 newtons.[2]

In common usage and other contexts, it is most often referred to in the United States as a pound or as lb, but this can lead to confusion with the pound-mass.

## Definition in terms of the SI unit of force[edit]

The newton (symbol: N) is the unit of force named in the International System of Units (SI). Using the standard average acceleration due to gravity, denoted gn, as being 9.80665 m/s2 and the internationally agreed upon definition of the pound-mass, denoted as lbm, as being 0.45359237 kg,[1][3] we can determine the number of newtons exactly equivalent to a pound-force:

1 l b f ≡ 1 l b m ⋅ g n ≡ 0.45359237 k g ⋅ 9.80665 m / s 2 ≡ 4.4482216152605 N {\displaystyle {\begin{aligned}1\,\mathrm {lbf} &\equiv 1\,\mathrm {lbm} \cdot g_{n}\\\&\equiv 0.45359237\,\mathrm {kg} \cdot 9.80665\,\mathrm {{m}/{s^{2}}} \\\&\equiv 4.4482216152605\,\mathrm {N} \end{aligned}}}

## Equivalent units of force[edit]

* 1 lbf ≈ 4.448221 newton (symbol: N)
* 1 lbf ≈ 4448822 dyne (symbol: dyn)
* 1 lbf ≈ 0.453592 kilogram-force (symbol: kgf)
* 1 lbf ≈ 0.453592 kilopond (symbol: kp)[note 2]
* 1 lbf ≈ 4.448221×10−3 sthène (symbol: sn)
* 1 lbf ≈ 32.17405 poundal (symbol: pdl)
* 1 lbf ≡ 0.001 kip (symbol: kip)[note 3]

## Notes[edit]

1. ↑ The symbol lbf is derived from the Latin libra for "pound" and the symbol f for "force")
2. ↑ Another name for a kilogram-force. Not to be confused with "kilopounds", meaning 1,000 pounds of mass.
3. ↑ A non-SI unit of force equal to 1,000 pound-force.

## References[edit]

1. ↑ 1.0 1.1 Resolution of the 3rd meeting of the CGPM (1901) Definition of the standard average acceleration due to gravity
2. ↑ Metric Conversion Table Scroll down to "Force"
3. ↑ Appendix 8, Customary System of Weights and Measures U.S. Dept. of Commerce, July 15, 1968. Definition of the pound-mass.