| Newton-metre | |
| Standard: | SI |
| Quantity: | torque |
| Symbol: | N⋅m |
| Symbol2: | N m |
| Units1: | FPS system |
| Inunits1: | 0.73756215 lbf.ft |
| Units2: | inch⋅pound-force |
| Inunits2: | 8.8507 in lbf |
| Units3: | inch⋅ounce-force |
| Inunits3: | 141.6 in oz |
The newton-metre or newton-meter (also non-hyphenated, newton metre or newton meter; symbol N⋅m[1] or N m[1]) is the unit of torque (also called) in the International System of Units (SI). One newton-metre is equal to the torque resulting from a force of one newton applied perpendicularly to the end of a moment arm that is one metre long.
The unit is also used less commonly as a unit of work, or energy, in which case it is equivalent to the more common and standard SI unit of energy, the joule.[2] In this usage the metre term represents the distance travelled or displacement in the direction of the force, and not the perpendicular distance from a fulcrum as it does when used to express torque. This usage is generally discouraged,[3] since it can lead to confusion as to whether a given quantity expressed in newton-metres is a torque or a quantity of energy. "Even though torque has the same dimension as energy (SI unit joule), the joule is never used for expressing torque".[4]
Newton-metres and joules are dimensionally equivalent in the sense that they have the same expression in SI base units,
1N{ ⋅ }m=1
| kg{ ⋅ | |
| m |
2}{s2} , 1J=1
| kg{ ⋅ | |
| m |
2}{s2}
but are distinguished in terms of applicable kind of quantity, to avoid misunderstandings when a torque is mistaken for an energy or vice versa. Similar examples of dimensionally equivalent units include Pa versus J/m3, Bq versus Hz, and ohm versus ohm per square.