Tonne

Template:Short description Template:Redirect-several Template:Infobox unit

The tonne (Template:IPAc-en or Template:IPAc-en; symbol: t) is a unit of mass equal to 1,000 kilograms. It is a non-SI unit accepted for use with SI.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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 (United States customary units) and the long ton (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 abbreviationsEdit

The BIPM symbol for the tonne is t, adopted at the same time as the unit in 1879.<ref name=bippy>Table 6 Template:Webarchive. BIPM. Retrieved on 2011-07-10.</ref> 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 (NIST).<ref name=fedreg/><ref>NIST Special Publication 330, 2019 edition states "The name of the unit with symbol t and defined according to 1 t = 10³ kg is called 'metric ton' rather than 'tonne.'".</ref> 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 units of energy, one megatonne of TNT is equivalent to approximately 4.184 petajoules.

Origin and spellingEdit

In English, tonne is an established spelling alternative to metric ton.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In American English and British English, tonne is usually pronounced the same as ton (Template:IPAc-en), but the final "e" can also be pronounced, i.e. "tunnie" (Template:IPAc-en).<ref>The Oxford English dictionary 2nd ed. lists both /tʌn/ and /ˈtʌni/</ref> In Australian English, the common and recommended pronunciation is Template:IPAc-en.<ref>Template:Cite book</ref><ref>Template:Cite news</ref> In the United States, metric ton is the name for this unit used and recommended by NIST;<ref name="fedreg">Metric System of Measurement: Interpretation of the International System of Units for the United States Template:Webarchive (PDF). See corrections in the Errata section of [1] Template:Webarchive.</ref> an unqualified mention of a ton typically refers to a short ton of 2,000 lb (907.2 kg) and to a lesser extent to a long ton of 2,240 lb (1,016 kg), with the term tonne rarely used in speech or writing. Both terms are acceptable in Canadian English.

Ton and tonne are both derived from a Germanic word in general use in the North Sea area since the Middle Ages (Template:Cf. Old English and Old Frisian tunne, Old High German and Medieval Latin {{#invoke:Lang|lang}}, German and French tonne) to designate a large cask, or tun.<ref>Template:OEtymD</ref> 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 spelling tonne pre-dates the introduction of the SI in 1960; it has been used with this meaning in France since 1842,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }} "Tonne" is listed under "The Principal Metric Units of Measurement" on p. 7. </ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }} "Tonne" is listed under Schedule 1, Part 3 as a non-SI unit of measurement used with SI units of measurement.</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In the United States, the unit was originally referred to using the French words millier or tonneau,<ref>Act of 28 July 1866, codified in Template:UnitedStatesCode</ref> but these terms are now obsolete.<ref name="FR1998">Template:Cite journal</ref> 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 tonneEdit

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.<ref>Template:Cite book</ref>

ConversionsEdit

One tonne is equivalent to:

Template:Val by definition.<ref>Template:SIbrochure9th</ref>
Template:Val or 1 megagram (Mg). Megagram is the corresponding official SI unit with the same mass. Mg is distinct from mg, milligram.
In pounds: Exactly Template:Sfrac pounds (lb) by definition of the pound,<ref name=nbs447>Template:Cite book</ref> or approximately Template:Val.<ref name=NGS>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

In short tons: Exactly Template:Sfrac short tons (tn), or approximately Template:Val tn.
- One short ton is exactly Template:Val.<ref name="NISTUnits">National Institute of Standards and Technology. Template:Cite book</ref>
In long tons: Exactly Template:Sfrac long tons (LT), or approximately Template:Val LT.
- One long ton is exactly Template:Val.<ref name="NISTUnits" />

A tonne is the mass of one cubic metre of pure water at Template:Convert.Template:Efn

Derived unitsEdit

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.Template:Efn

Tonnes		Grams		Equivalents<ref group="table">The equivalent units columns use the short scale large-number naming system currently used in most English-language countries, e.g. 1 billion = 1000 million = Template:Val.</ref>
Name	Symbol	Name	Symbol	Tonnes (t)	Short Tons (tn)<ref name="rounding" group="table">Values in the equivalent short and long tons columns are rounded to five significant figures. See Conversions for exact values.</ref>	Long Tons (LT)<ref name="rounding" group="table"/>
tonne	t	megagram	Mg	1 t	Template:Convert tn	Template:Convert LT
kilotonne	kt<ref group="table">Though non-standard, the symbol "kt" is also used (instead of the standard symbol "kn") for knot, a unit of speed for aircraft and watercraft. The standard meaning of the symbol kt is for kilotonne.</ref>	gigagram	Gg	1,000 t	Template:Convert tn	Template:Convert LT
megatonne	Mt	teragram	Tg	1,000,000 t	Template:Convert million tn	Template:Convert LT
gigatonne	Gt	petagram	Pg	1,000,000,000 t	Template:Convert billion tn	Template:Convert million LT

Alternative usagesEdit

Metric ton unitsEdit

A metric ton unit (mtu) can mean Template:Convert 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>How Many? A Dictionary of Units of Measurement Template:Webarchive. Unc.edu. Retrieved on 2011-07-10.</ref> The following excerpt from a mining geology textbook describes its usage in the particular case of tungsten: Template:Quote

In the case of uranium, MTU is sometimes used in the sense of metric ton of uranium (Template:Convert).<ref>Reference.Pdf. (PDF) . Retrieved on 2011-07-10.</ref><ref>"Glossary Template:Webarchive". (June 2000). Disposition of Surplus Hanford Site Uranium, Hanford Site, Richland, Washington. US Department of Energy.</ref><ref>"Acronyms Template:Webarchive". Y-12 National Security Complex.</ref><ref>NRC Collection of Abbreviations (NUREG-0544, Rev. 4), United States Nuclear Regulatory Commission. Nrc.gov (2011-03-13). Retrieved on 2011-07-10.</ref>

Use of mass as proxy for energyEdit

Template:Main article

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 = Template:Abbr 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. One tonne of TNT is approximately 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 forceEdit

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. 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.