The tonne (/tʌn/ ( listen)) (Non-SI unit, symbol: t), commonly referred to as the metric ton in the United States, is a non-SI metric unit of mass equal to 1,000 kilograms; or one megagram (Mg); it is equivalent to approximately 2,204.6 pounds, 1.102 short tons (US) or 0.984 long tons (imperial). Although not part of the SI, the tonne is accepted for use with SI units and prefixes by the International Committee for Weights and Measures.
1 Symbol and abbreviations 2 Origin and spelling 3 Conversions 4 Derived units 5 Alternative usage
5.1 Use of mass as proxy for energy 5.2 Unit of force
6 See also 7 Notes and references 8 External links
Symbol and abbreviations
The SI symbol for the tonne is "t", adopted at the same time as the
unit in 1879. Its use is also official for the metric ton in the
United States, having been adopted by the United States National
Institute of Standards and Technology. It is a symbol, not an
abbreviation, and should not be followed by a period. Informal and
non-approved symbols or abbreviations include "T", "mT", "MT", and
"mt". Some of these are SI symbols for other units: "T" is the SI
symbol for the tesla and "Mt" is the SI symbol for megatonne
(equivalent to one teragram); if describing
Metric/SI: 1 megagram (Mg) (by definition). Equal to 7006100000000000000♠1000000 grams (g) or 7003100000000000000♠1000 kilograms (kg).
Megagram, Mg, is the official SI unit. Mg is distinct from mg, milligram.
Pounds (lb): Exactly 1000/0.453 592 37 lb (by definition of the pound), or approximately 7003100000000006859♠2204.622622 lb (10 s.f.). US/Short tons (ST): Exactly 1/0.907 184 74 short tons, or approximately 7000110231131100000♠1.102311311 ST (10 s.f.).
One short ton is exactly 7002907184740000000♠0.90718474 t.
Imperial/Long tons (LT): Exactly 1/1.016 046 9088 long tons, or approximately 6999984206527600000♠0.9842065276 LT (10 s.f.).
One long ton is exactly 7003101604690880000♠1.0160469088 t.
Derived units For multiples of the tonne, it is more usual to speak of thousands or millions of tonnes. Kilotonne, megatonne, and gigatonne are more usually used for the energy of nuclear explosions and other events, often loosely as approximate figures. When used in this context, there is little need to distinguish between metric and other tons, and the unit is spelt either as ton or tonne with the relevant prefix attached.
Tonnes Grams Equivalents*
Multiple Name Symbol Multiple Name Symbol Tonnes (t) Kilograms (kg) Grams (g) US/short tons (ST)† Imperial/long tons (LT)†
100 Tonne t 106 Megagram Mg 1 t 1,000 kg 1 million g 1.1023 ST 0.98421 LT
103 Kilotonne ktǂ 109 Gigagram Gg 1,000 t 1 million kg 1 billion g 1,102.3 ST 984.21 LT
106 Megatonne Mt 1012 Teragram Tg 1 million t 1 billion kg 1 trillion g 1.1023 million ST 984,210 LT
109 Gigatonne Gt 1015 Petagram Pg 1 billion t 1 trillion kg 1 quadrillion g 1.1023 billion ST 984.21 million LT
1012 Teratonne Tt 1018 Exagram Eg 1 trillion t 1 quadrillion kg 1 quintillion g 1.1023 trillion ST 984.21 billion LT
1015 Petatonne Pt 1021 Zettagram Zg 1 quadrillion t 1 quintillion kg 1 sextillion g 1.1023 quadrillion ST 984.21 trillion LT
1018 Exatonne Et 1024 Yottagram Yg 1 quintillion t 1 sextillion kg 1 septillion g 1.1023 quintillion ST 984.21 quadrillion LT
*The equivalent units columns use the short scale large-number naming system currently used in most English-language countries, e.g. 1 billion = 1,000 million = 1,000,000,000. †Values in the equivalent short and long tons columns are rounded to five significant figures, see Conversions for exact values. ǂThough non-standard, the symbol "kt" is also used for knot, a unit of speed for aircraft and sea-going vessels, and should not be confused with kilotonne. Alternative usage A metric ton unit (MTU) can mean 10 kilograms (22 lb) within metal (e.g. tungsten, manganese) trading, particularly within the US. It traditionally referred to a metric ton of ore containing 1% (i.e. 10 kg) of metal. In the case of uranium, the acronym MTU is sometimes considered to be metric ton of uranium, meaning 1,000 kg. A gigatonne of carbon dioxide equivalent (GtCO2eq) is a unit used by the UN climate change panel, IPCC, to measure the effect of a technology or process on global warming. Use of mass as proxy for energy Main article: TNT equivalent The tonne of trinitrotoluene (TNT) is used as a proxy for energy, usually of explosions (TNT is a common high explosive). Prefixes are used: kiloton(ne), megaton(ne), gigaton(ne), especially for expressing nuclear weapon yield, based on a specific combustion energy of TNT of about 4.2 MJ/kg (or one thermochemical calorie per milligram). Hence, 1 t TNT = 4.2 GJ, 1 kt TNT = 4.2 TJ, 1 Mt TNT = 4.2 PJ. The SI unit of energy is the joule. Assuming that a TNT explosion releases 1,000 small (thermochemical) calories per gram (4.2 kJ/g), one tonne of TNT is equivalent to 4.2 gigajoules. In the petroleum industry the tonne of oil equivalent (toe) is a unit of energy: the amount of energy released by burning one tonne of crude oil, approximately 42 GJ. There are several slightly different definitions. This is ten times as much as a tonne of TNT because atmospheric oxygen is used. Unit of force Like the gram and the kilogram, the tonne gave rise to a (now obsolete) force unit of the same name, the tonne-force, equivalent to about 9.8 kilonewtons: a unit also often called simply "tonne" or "metric ton" without identifying it as a unit of force. In contrast to the tonne as a mass unit, the tonne-force or metric ton-force is not acceptable for use with SI, partly because it is not an exact multiple of the SI unit of force, the newton. See also
Metre–tonne–second system of units
Notes and references
^ Weights and Measures Act 1985. National Archives (London), 2014.
Accessed 13 Aug 2014.
^ a b Table 6 Archived 2009-10-01 at the Wayback Machine.. BIPM.
Retrieved on 2011-07-10.
^ a b "Metric System of Measurement: Interpretation of the
International System of Units
v t e
International System of Units
ampere candela kelvin kilogram metre mole second
Derived units with special names
becquerel coulomb degree Celsius farad gray henry hertz joule katal lumen lux newton ohm pascal radian siemens sievert steradian tesla volt watt weber
Other accepted units
astronomical unit bar dalton day decibel degree of arc electronvolt hectare hour litre minute minute of arc neper second of arc tonne atomic units natural units
Conversion of units Metric prefixes Proposed redefinitions Systems of measurement