The tonne ( or ; symbol: t) is a

unit of mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

equal to 1,000

kilogram The kilogram (also spelled kilogramme) is the base unit of mass in the International System of Units (SI), equal to one thousand grams. It has the unit symbol kg. The word "kilogram" is formed from the combination of the metric prefix kilo- (m ...

s. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the

short ton The short ton (abbreviation: tn or st), also known as the US ton, is a measurement unit equal to . It is commonly used in the United States, where it is known simply as a ton; however, the term is ambiguous, the single word "ton" being variously ...

(

United States customary units United States customary units form a system of measurement units commonly used in the United States and most U.S. territories since being standardized and adopted in 1832. The United States customary system developed from English units that ...

) and the

long ton The long ton, also known as the imperial ton, displacement ton,Dictionary.com - ''"a unit for measuring the displacement of a vessel, equal to a long ton of 2240 pounds (about 1016 kg) or 35 cu. ft. (1 cu. m) of seawater."'' or British ton, is a ...

( British imperial units). It is equivalent to approximately 2,204.6 pounds, 1.102 short tons, and 0.984 long tons. The official SI unit is the megagram (Mg), a less common way to express the same amount.

Symbol and abbreviations

The BIPM symbol for the tonne is t, adopted at the same time as the unit in 1879.Table 6
. BIPM. Retrieved on 2011-07-10. 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 The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into Outline of p ...

(NIST). It is a symbol, not an abbreviation, and should not be followed by a period. Use of lower case is significant, and use of other letter combinations can lead to ambiguity. For example, T, MT, mT, are the SI symbols for the tesla, megatesla, and millitesla, respectively, while Mt and mt are SI-compatible symbols for the megatonne (one teragram) and millitonne (one kilogram). If describing

TNT equivalent TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. A ton of TNT equivalent is a unit of energy defined by convention to be (). It is the approximate energy released in the de ...

units of energy, one megatonne of TNT is equivalent to approximately 4.184

petajoule The joule ( , or ; symbol: J) is the unit of energy in the International System of Units (SI). In terms of SI base units, one joule corresponds to one kilogram-metre, metre squared per second, second squared One joule is equal to the amount ...

Origin and spelling

In English, ''tonne'' is an established spelling alternative to ''metric ton''. In American English and British English, tonne is usually pronounced the same as ton (), but the final "e" can also be pronounced, i.e. "tunnie" (). In Australian English, the common and recommended pronunciation is . In the United States, ''metric ton'' is the name for this unit used and recommended by NIST;Metric System of Measurement: Interpretation of the International System of Units for the United States
(PDF). See corrections in the Errata section o

. an unqualified mention of a ''ton'' typically refers to a

of 2,000 lb (907.2 kg) and to a lesser extent to a

of 2,240 lb (1,016 kg), with the term ''tonne'' rarely used in speech or writing. Both terms are acceptable in

Canadian English Canadian English (CanE, CE, en-CA) encompasses the Variety (linguistics), varieties of English language, English used in Canada. According to the 2016 Canadian Census, 2016 census, English was the first language of 19.4 million Canadians or ...

. ''Ton'' and ''tonne'' are both derived from a Germanic word in general use in the

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

area since the

Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...

(

Old English Old English ( or , or ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the Early Middle Ages. It developed from the languages brought to Great Britain by Anglo-S ...

and

Old Frisian Old Frisian was a West Germanic language spoken between the late 13th century and the end of 16th century. It is the common ancestor of all the modern Frisian languages except for the North Frisian language#Insular North Frisian, Insular North ...

''tunne'',

Old High German Old High German (OHG; ) is the earliest stage of the German language, conventionally identified as the period from around 500/750 to 1050. Rather than representing a single supra-regional form of German, Old High German encompasses the numerous ...

and

Medieval Latin Medieval Latin was the form of Literary Latin used in Roman Catholic Church, Roman Catholic Western Europe during the Middle Ages. It was also the administrative language in the former Western Roman Empire, Roman Provinces of Mauretania, Numidi ...

German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...

and French ''tonne'') to designate a large cask, or ''tun''. A full tun, standing about a metre high, could easily weigh a tonne. See also the common German word :de:Mülltonne (literal translation: garbage

drum The drum is a member of the percussion group of musical instruments. In the Hornbostel–Sachs classification system, it is a membranophone. Drums consist of at least one membrane, called a drumhead or drum skin, that is stretched over a ...

). The spelling ''tonne'' pre-dates the introduction of the SI in 1960; it has been used with this meaning in France since 1842, when there were no metric prefixes for multiples of 10⁶ and above, and is now used as the standard spelling for the metric mass measurement in most English-speaking countries. In the United States, the unit was originally referred to using the French words ''millier'' or ''tonneau'', but these terms are now obsolete. The British imperial and United States customary units are comparable to the ''tonne'' and the spelling of ''ton'' in English is the same, though they differ in mass.

French pre-metric tonne

Prior to metrification the French tonne consisted of 2000 French pounds (livres). Therefore a French tonne of that era weighed 979 kg compared to an English ton of 1016 kg. Prior to the use of tonne for this weight tonneau (plural: tonneaux) was used.

Conversions

One tonne is equivalent to: * by definition. * or 1 megagram (Mg). Megagram is the corresponding official SI unit with the same mass. Mg is distinct from mg, milligram. *In pounds: Exactly pounds (lb) by definition of the pound, or approximately . *In

s: Exactly short tons (tn), or approximately tn. **One short ton is exactly .National Institute of Standards and Technology. *In

s: Exactly long tons (LT), or approximately LT. **One long ton is exactly . A tonne is the mass of one

cubic metre The cubic metre (in Commonwealth English and international spelling as used by the International Bureau of Weights and Measures) or cubic meter (in American English) is the unit of volume in the International System of Units (SI). Its symbol is m ...

of pure water at .

Derived units

As a non-SI unit, the use of SI metric prefixes with the tonne does not fall within the SI standard. 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 in equivalent mass of TNT, 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 spelled either as ''ton'' or ''tonne'' with the relevant prefix attached.

Alternative usages

Metric ton units

A metric ton unit (mtu) can mean within metal trading, particularly within the United States. It traditionally referred to a metric ton of ore containing 1% (i.e. 10 kg) of metal. The following excerpt from a mining geology textbook describes its usage in the particular case of tungsten: In the case of

uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...

, ''MTU'' is sometimes used in the sense of ''metric ton of uranium'' ().NRC Collection of Abbreviations (NUREG-0544, Rev. 4), United States Nuclear Regulatory Commission
Nrc.gov (2011-03-13). Retrieved on 2011-07-10.

Use of mass as proxy for energy

The ''tonne of

trinitrotoluene Troponin T (shortened TnT or TropT) is a part of the troponin complex, which are proteins integral to the contraction of skeletal and heart muscles. They are expressed in skeletal and cardiac myocytes. Troponin T binds to tropomyosin and help ...

(TNT)'' is used as a proxy for energy, usually of explosions (TNT is a common

high explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...

). Prefixes are used: kiloton(ne), megaton(ne), gigaton(ne), especially for expressing

nuclear weapon yield The explosive yield of a nuclear weapon is the amount of energy released such as blast, thermal, and nuclear radiation, when that particular nuclear weapon is detonated. It is usually expressed as a ''TNT equivalent'', the standardized equivalen ...

, based on a specific combustion energy of TNT of about 4.2 MJ/ kg (or one thermochemical calorie per

milligram The kilogram (also spelled kilogramme) is the base unit of mass in the International System of Units (SI), equal to one thousand grams. It has the unit symbol kg. The word "kilogram" is formed from the combination of the metric prefix kilo- (m ...

). Hence, 1 t TNT = 4.2 GJ, 1 kt TNT = approx. 4.2 TJ, 1 Mt TNT = approx. 4.2 PJ. The SI unit of energy is the

joule The joule ( , or ; symbol: J) is the unit of energy in the International System of Units (SI). In terms of SI base units, one joule corresponds to one kilogram- metre squared per second squared One joule is equal to the amount of work d ...

. One tonne of TNT is approximately equivalent to 4.2 gigajoules. In the

petroleum industry The petroleum industry, also known as the oil industry, includes the global processes of hydrocarbon exploration, exploration, extraction of petroleum, extraction, oil refinery, refining, Petroleum transport, transportation (often by oil tankers ...

, the

tonne of oil equivalent The tonne of oil equivalent (abbreviated toe) is a unit of energy defined as the amount of energy released by burning one tonne of crude oil. It is approximately 42 gigajoules or 11.630 megawatt-hours, although as different crude oils have diffe ...

(toe) is a

unit of energy Energy is defined via work, so the SI unit of energy is the same as the unit of work – the joule (J), named in honour of James Prescott Joule and his experiments on the mechanical equivalent of heat. In slightly more fundamental terms, ...

: the amount of energy released by burning one tonne of

crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...

, 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 The gram (originally gramme; SI unit symbol g) is a Physical unit, unit of mass in the International System of Units (SI) equal to one thousandth of a kilogram. Originally defined in 1795 as "the absolute Mass versus weight, weight of a volume ...

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. The unit is 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 is not accepted for use with SI.

Notes and references

;Notes ;Citations

External links

*NIST Special Publication 811
''Guide for the Use of the International System of Units (SI)''
{{authority control Non-SI metric units Units of mass