View source for Tonne

{{Short description|Metric unit of mass equivalent to 1,000 kilograms or 1 megagram}}
{{Redirect-several|dab=off|Ton (disambiguation)|Tonne (disambiguation)|Megagram (geometry)|Gigaton (album){{!}}''Gigaton'' (album)}}
{{Infobox unit
| bgcolor    = 
| name       = Tonne<br>{{Small|Megagram}}
| image      = File:A 1-tonne weight (geograph 6511341).jpg
| caption    = A one-tonne (1000-kilogram) concrete block
| standard   = [[Non-SI units mentioned in the SI|Non-SI]]
| quantity   = mass
| symbol     = t <br> Mg
| extralabel = In [[SI unit]]s:
| extradata  = {{Val|1000|u=kg}}
}}

The '''tonne''' ({{IPAc-en|audio=En-us-tonne.ogg|t|ʌ|n}} or {{IPAc-en|t|ɒ|n}}; symbol:&nbsp;'''t''') is a [[unit of mass]] equal to 1,000&nbsp;[[kilogram]]s. It is a [[Non-SI units mentioned in the SI|non-SI unit accepted for use with SI]].<ref>{{cite web|url=https://web.archive.org/web/20200316121104/https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9-EN.pdf|work=Bureau International de Poids et Mesures|title=Non-SI units accepted for use with the SI, and units based on fundamental constants|pages=145-146}}</ref> It is also referred to as a '''metric ton''' in the United States to distinguish it from the [[ton|non-metric unit]]s of the [[short ton]] ([[United States customary units]]) and the [[long ton]] ([[Imperial units|British imperial units]]). It is equivalent to approximately 2,204.6 [[international avoirdupois pound|pound]]s, 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 [[International Bureau of Weights and Measures|BIPM]] symbol for the tonne is t, adopted at the same time as the unit in 1879.<ref name=bippy>[http://www.bipm.org/en/si/si_brochure/chapter4/table6.html Table 6] {{webarchive|url=https://web.archive.org/web/20091001100650/http://www.bipm.org/en/si/si_brochure/chapter4/table6.html |date=2009-10-01 }}. 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>[[National Institute of Standards and Technology|NIST]] [https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.330-2019.pdf Special Publication 330, 2019 edition] states "The name of the unit with symbol t and defined according to 1 t = 10<SUP>3</SUP> kg is called 'metric ton' rather than 'tonne.'".</ref> It is a symbol, not an abbreviation, and should not be followed by a [[period (punctuation)|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 (unit)|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 [[petajoule]]s.

==Origin and spelling==

In English, ''tonne'' is an established spelling alternative to ''metric ton''.<ref>{{cite web |url=https://www.oed.com/view/Entry/203217?redirectedFrom=tonne#eid |title=tonne, n |work=[[OED]] |access-date=6 August 2021}}</ref> In American English and British English, tonne is usually pronounced the same as ton ({{IPAc-en|t|ʌ|n}}), but the final "e" can also be pronounced, i.e. "tunnie" ({{IPAc-en|ˈ|t|ʌ|n|i}}).<ref>The Oxford English dictionary 2nd ed. lists both /tʌn/ and /ˈtʌni/</ref> In Australian English, the common and recommended pronunciation is {{IPAc-en|t|ɒ|n}}.<ref>{{cite book |title= Macquarie Dictionary|edition= fifth |year= 2009|publisher= Macquarie Dictionary Publishers Pty Ltd|location= Sydney}}</ref><ref>{{cite news |date=1972-11-21 |title=How To Pronounce Metrics Units (advertisement by Australian Metric Conversion Board) |work=The Age |page=14 |access-date=2021-11-01 |url=https://news.google.com/newspapers?id=9ihVAAAAIBAJ&sjid=3ZADAAAAIBAJ&pg=6434%2C4864047}}</ref> In the United States, ''metric ton'' is the name for this unit used and recommended by NIST;<ref name="fedreg">[http://lamar.colostate.edu/~hillger/laws/63fr40333.pdf Metric System of Measurement: Interpretation of the International System of Units for the United States] {{Webarchive|url=https://web.archive.org/web/20080409102714/http://lamar.colostate.edu/~hillger/laws/63fr40333.pdf|date=2008-04-09}} (PDF). See corrections in the Errata section of [http://lamar.colostate.edu/~hillger/laws/nist-interpretation.html] {{Webarchive|url=https://web.archive.org/web/20080418115704/http://lamar.colostate.edu/~hillger/laws/nist-interpretation.html|date=2008-04-18}}.</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 languages|Germanic]] word in general use in the [[North Sea]] area since the [[Middle Ages]] ({{cf.}} [[Old English]] and [[Old Frisian]] {{Lang|ofs|tunne}}, [[Old High German]] and [[Medieval Latin]] {{Lang|la-x-medieval|tunna}}, [[German language|German]] and [[French language|French]] {{Lang|fr|tonne}}) to designate a large cask, or ''tun''.<ref>{{OEtymD|tonne}}</ref> A full tun, standing about a metre high, could easily weigh a tonne. See also the common German word {{lang|de|[[wikt:Mülltonne|Mülltonne]]}} ({{literal translation|garbage [[Drum (container)|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>{{cite web|url=http://atilf.atilf.fr/dendien/scripts/tlfiv4/showps.exe?p=combi.htm;java=no;|title=Recherche d'un mot|website=atilf.atilf.fr}}</ref> when there were no metric prefixes for multiples of 10<sup>6</sup> and above, and is now used as the standard spelling for the metric mass measurement in most [[English language|English]]-speaking countries.<ref>{{cite web
|url=http://www.nmo.bis.gov.uk/Docs/Legislation/Units%20of%20Measurement/Gnotes%20for%20public%20sector%20on%20use%20of%20metric.pdf
|title=Guidance Note on the use of Metric Units of Measurement by the Public Sector
|year=2007
|publisher=National Measurement Office
|access-date=2010-02-13
|url-status=dead
|archive-url=http://webarchive.nationalarchives.gov.uk/20110207120946/http://www.nmo.bis.gov.uk/Docs/Legislation/Units%20of%20Measurement/Gnotes%20for%20public%20sector%20on%20use%20of%20metric.pdf
|archive-date=2011-02-07
}}  "Tonne" is listed under "The Principal Metric Units of Measurement" on p. 7.
</ref><ref>{{cite web
|url=  http://www.comlaw.gov.au/ComLaw/Legislation/LegislativeInstrumentCompilation1.nsf/framelodgmentattachments/35F21696B4C9E27CCA2575EC001FA5D1
|title= National Measurement Regulations 1999 {{pipe}}|year=1999
|publisher=Australian Government
|access-date=2010-02-13}} "Tonne" is listed under Schedule 1, Part 3 as a non-SI unit of measurement used with SI units of measurement.</ref><ref>{{cite web |url= http://www.maf.govt.nz/statistics/forestry/annual/nzstats2000/appendix/append4.htm|title= Appendix 4: Units of Measurement and Conversion Factors|publisher= MAF (Ministry of Agriculture and Forestry (New Zealand))|access-date=2010-02-13}}</ref><ref>{{cite web|url=http://www.gazette.gc.ca/archives/p2/1999/1999-11-10/html/sor-dors430-eng.html|title=Canada Gazette|date=1998–2007|publisher=Government of Canada|access-date=2010-02-13|quote=The Corporation shall pay to producers selling and delivering wheat produced in the designated area to the Corporation the following sums certain per tonne basis...|archive-date=2011-07-06|archive-url=https://web.archive.org/web/20110706181616/http://www.gazette.gc.ca/archives/p2/1999/1999-11-10/html/sor-dors430-eng.html|url-status=dead}}</ref> In the United States, the unit was originally referred to using the [[French language|French]] words {{Lang|fr|millier}} or {{Lang|fr|tonneau}},<ref>Act of 28 July 1866, codified in {{UnitedStatesCode|15|205}}</ref> but these terms are now obsolete.<ref name="FR1998">{{cite journal |title=Metric System of Measurement: Interpretation of the International System of Units for the United States |journal=[[Federal Register]] |date=28 July 1998 |volume=63 |issue=144 |id=63 FR 40333 |page=40338 |url=http://physics.nist.gov/cuu/pdf/SIFedReg.pdf |url-status    = dead |archive-url=https://web.archive.org/web/20111015081850/http://physics.nist.gov/cuu/pdf/SIFedReg.pdf |archive-date=15 October 2011}}</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 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.<ref>{{cite book |last1=Winfield |first1=Rif |last2=Roberts |first2=Stephen S. |title=French warships in the age of sail 1626-1786: design, construction, careers and fates |date=2017 |publisher=Seaforth Publishing |location=Barnsley, South Yorkshire |isbn=978-1-4738-9351-1 |page=2}}</ref>

==Conversions==
One tonne is equivalent to:
*{{val|1000|u=[[kilogram]]s&nbsp;(kg)}} by definition.<ref>{{SIbrochure9th}}</ref>
*{{val|1000000|u=[[gram]]s&nbsp;(g)}} or 1 megagram (Mg). Megagram is the corresponding official SI unit with the same mass; it is rarely used, in part because the base SI unit of mass is the kilogram, not the gram. Mg is distinct from mg, milligram.
*{{sfrac|1000|0.453{{thin space}}592{{thin space}}37}} [[Pound (mass)|pounds]] (lb), by definition of the pound,<ref name=nbs447>{{Cite book | title=Weights and measures standards of the United States – A brief history | year=1976 | url=http://physics.nist.gov/Pubs/SP447/contents.html | first=L. E. | last=Barbrow | last2=Judson |first2=L. V. | url-status=dead | archive-url=https://web.archive.org/web/20080511153143/http://physics.nist.gov/Pubs/SP447/contents.html | archive-date=2008-05-11 }}</ref> or approximately {{val|2204.622622|u=lb}}.<!-- By calculation--><ref name=NGS>{{cite web | url= http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf  | author        = United States National Bureau of Standards  | title= Notices 'Refinement of values for the yard and the pound' | date= 1959-06-25 | access-date= 2006-08-12}}</ref>
*{{sfrac|1|0.907{{thin space}}184{{thin space}}74}}&nbsp;[[short&nbsp;tons]] (tn), exactly, or approximately {{val|1.102311311}}&nbsp;tn.<!-- By calculation-->
**One short ton is exactly {{val|0.90718474|u=t}}.<ref name="NISTUnits">National Institute of Standards and Technology. {{cite book |date=October 2013 |chapter=Appendix C – General Tables of Units of Measurement |chapter-url=https://www.nist.gov/pml/wmd/pubs/upload/appc-14-hb44-final.pdf |editor1-last=Butcher |editor1-first=Tina |editor2-last=Crown |editor2-first=Linda |editor3-last=Harshman |editor3-first=Rick |editor4-last=Williams |editor4-first=Juana |title=Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices |url=https://www.nist.gov/pml/wmd/pubs/hb44-14.cfm |series=NIST Handbook |volume=44 |edition=2014 |location=Washington, D.C. |publisher=U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology |page=C-13 |issn=0271-4027 |oclc=58927093 |access-date=10 December 2013}}</ref>
*{{sfrac|1|1.016{{thin space}}046{{thin space}}9088}}&nbsp;[[long&nbsp;tons]] (LT), exactly, or approximately {{val|0.9842065276}}&nbsp;LT.<!-- By calculation-->
**One long ton is exactly {{val|1.0160469088|u=t}}.<ref name="NISTUnits" />

A tonne is the mass of one [[cubic metre]] of pure water at {{convert|4|C}}.{{efn|To within 0.003%.}}

==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 [[TNT equivalent|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.{{efn|The Oxford English Dictionary 2nd ed. gives both megaton and megatonne and adds "The unit may be calculated in either imperial or metric tons; the form megatonne generally implies the metric unit". The use for energy is the first definition; use for mass or weight is the third definition.}}
{|class="wikitable" style="text-align:center"
|-
! colspan=2 | Tonnes
! colspan=2 | Grams
! colspan=3 | 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&nbsp;billion = 1000&nbsp;million = {{val|1,000,000,000}}.</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 [[Rounding|rounded]] to five [[significant figures]]. See [[#Conversions|Conversions]] for exact values.</ref> !! Long Tons (LT)<ref name="rounding" group="table"/>
|-
|     tonne  ||t
|  megagram  ||Mg
|1 t                || {{convert|1|t|ST|disp=output number only|sigfig=5|comma=gaps}}&nbsp;tn || {{convert|1|t|LT|disp=output number only|sigfig=5|comma=gaps}}&nbsp;LT
|-
| kilotonne  ||kt<ref group="table">Though non-standard, the symbol "kt" is also used (instead of the standard symbol "kn") for [[knot (unit)|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            || {{convert|1000|t|ST|disp=output number only|sigfig=5|comma=gaps}}&nbsp;tn || {{convert|1000|t|LT|disp=output number only|sigfig=5|comma=gaps}}&nbsp;LT
|-
| [[Orders of magnitude (mass)#106 to 1011 kg|megatonne]]  ||Mt
|  teragram  ||Tg
| 1,000,000 t  || {{convert|1|t|ST|disp=output number only|sigfig=5|comma=gaps}}&nbsp;million&nbsp;tn || {{convert|1000000|t|LT|disp=output number only|sigfig=5|comma=gaps}}&nbsp;LT
|-
| gigatonne||Gt
|  petagram||Pg
| 1,000,000,000 t  || {{convert|1|t|ST|disp=output number only|sigfig=5|comma=gaps}}&nbsp;billion&nbsp;tn || {{convert|1000|t|LT|disp=output number only|sigfig=5|comma=gaps}}&nbsp;million&nbsp;LT
|}

<references group=table/>

==Alternative usages==
===Metric ton units=== <!--[[MOS:NOBACKREF]] notwithstanding-->
A '''metric ton unit''' (mtu) can mean {{convert|10|kg|abbr=on}} within metal trading, particularly within the United States. It traditionally referred to a metric ton of ore containing 1% (i.e. 10&nbsp;kg) of metal.<ref>{{cite web|url=http://www.emis.platts.com/thezone/guides/platts/metals/conversion.html|title=Platt's Metals Guide to Specifications – Conversion Tables|date=8 September 2008|url-status=bot: unknown|archive-url=https://web.archive.org/web/20080908055702/http://www.emis.platts.com/thezone/guides/platts/metals/conversion.html|archive-date=8 September 2008}}</ref><ref>[http://www.unc.edu/~rowlett/units/dictM.html How Many? A Dictionary of Units of Measurement] {{Webarchive|url=https://web.archive.org/web/20110904024909/http://www.unc.edu/~rowlett/units/dictM.html |date=2011-09-04 }}. 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:
{{quote|
Tungsten concentrates are usually traded in metric tonne units (originally designating one tonne of ore containing 1% of WO<sub>3</sub>, today used to measure WO<sub>3</sub> quantities in 10 kg units. One metric tonne unit (mtu) of tungsten (VI) contains 7.93 kilograms of tungsten.|Walter L Pohl, ''Economic Geology: Principles and Practices'', English edition, 2011, p 183.}}

In the case of [[uranium]], ''MTU'' is sometimes used in the sense of ''metric ton of uranium'' ({{convert|1,000|kg|abbr=on|disp=sqbr}}).<ref>[http://www-pub.iaea.org/MTCD/publications/PDF/rwmp-3/REFERENCE.pdf Reference.Pdf]. (PDF) . Retrieved on 2011-07-10.</ref><ref>"[http://www.hanford.gov/rl/uploadfiles/ea/ea1319/ea1319.html Glossary] {{Webarchive|url=https://web.archive.org/web/20100314163903/http://www.hanford.gov/rl/uploadfiles/ea/ea1319/ea1319.html |date=2010-03-14 }}". (June 2000). ''Disposition of Surplus Hanford Site Uranium, Hanford Site, Richland, Washington''. US Department of Energy.</ref><ref>"[http://www.y12.doe.gov/library/acronyms/letter.php?index=M Acronyms] {{Webarchive|url=https://web.archive.org/web/20130312082236/http://www.y12.doe.gov/library/acronyms/letter.php?index=M |date=2013-03-12 }}". Y-12 National Security Complex.</ref><ref>[https://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0544/r4/ 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 energy===<!-- This section is linked from [[Impact event]] -->
{{Main article|TNT equivalent|Tonne of oil 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 [[Fuel value|specific combustion energy]] of TNT of about 4.2&nbsp;[[megajoule|MJ]]/[[kilogram|kg]] (or one [[calorie|thermochemical calorie]] per [[milligram]]).  Hence, 1 t TNT = {{abbr|approx.|approximately}} 4.2&nbsp;[[Gigajoule|GJ]], 1 [[kiloton|kt]] TNT = approx. 4.2&nbsp;[[Terajoule|TJ]], 1&nbsp;Mt TNT = approx. 4.2&nbsp;[[Petajoule|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 [[units of energy|unit of energy]]: the amount of energy released by burning one tonne of [[crude oil]], approximately 42&nbsp;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 [[Newton_(unit)#Kilonewtons|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.

==See also==
* [[Metre–tonne–second system of units]]
* [[Orders of magnitude (mass)]]
* [[Ton]]
** [[Tonnage]]
** [[Ton (volume)]]

== Notes and references ==
;Notes
{{notelist}}
;Citations
{{Reflist}}

== External links ==
*NIST Special Publication 811, [https://web.archive.org/web/20100216211152/http://physics.nist.gov/Pubs/SP811/ ''Guide for the Use of the International System of Units (SI)'']

{{SI units}}

{{authority control}}

[[Category:Non-SI metric units]]
[[Category:Units of mass]]