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A 'tonne' ('t') or 'metric ton' ('M/T'), sometimes referred to as a ''metric tonne'', is a measurement of mass equal to 1,000 kilograms. It is not an SI unit but is accepted for use with the SI.^[1] The proper SI unit for a tonne would be a "megagram" (Mg, see SI prefix), but this term is rarely used in practice. Though the spelling ''tonne'' predates the introduction of the SI system in 1960, it is now used as the standard spelling for the metric mass measurement in English. The similar Imperial units and United States customary units are spelled 'ton' in English.
This unit was defined in the United States in 1866^[2] as a ''millier'' or a ''tonneau''. However, neither of these are in use and though they still appear in the statute, they have been declared obsolete by NIST.^[3]

Contents

Definition

Multiples

Origin

Conversions

Explanation

Use of mass as proxy for energy

Metric ton in popular culture

Derived units

See also

References

Definition

1 tonne is defined as '1000 kilograms' or '1 megagram' (Mg, kilokilogram is incorrect per CIPM, 1967: Recommendation 2^[4])

Multiples

Multiple	Name	Symbol		Multiple	Name	Symbol		Multiple	Name	Symbol		Multiple	Name	Symbol
100	'tonne'	t		106	megagram	Mg		100	'tonne'	t		106	megagram	Mg
101	decatonne	dat		107	''(none)''	''(none)''		10–1	decitonne	dt		105	''(none)''	''(none)''
102	hectotonne	ht		108	''(none)''	''(none)''		10–2	centitonne	ct		104	''(none)''	''(none)''
103	kilotonne	kt		109	gigagram	Gg		10–3	millitonne	mt		103	kilogram	kg
106	megatonne	Mt		1012	teragram	Tg		10–6	microtonne	µt		100	gram	g
109	gigatonne	Gt		1015	petagram	Pg		10–9	nanotonne	nt		10-3	milligram	mg
1012	teratonne	Tt		1018	exagram	Eg		10–12	picotonne	pt		10-6	microgram	μ­g
1015	petatonne	Pt		1021	zettagram	Zg		10–15	femtotonne	ft		10-9	nanogram	ng
1018	exatonne	Et		1024	yottagram	Yg		10–18	attotonne	at		10-12	picogram	pg
1021	zettatonne	Zt		1027	''(none)''	''(none)''		10–21	zeptotonne	zt		10-15	femtogram	fg
1024	yottatonne	Yt		1030	''(none)''	''(none)''		10–24	yoctotonne	yt		10-18	attogram	ag

Origin

The spelling ''tonne'' is from French. In Old English the spelling was tunne. The various spellings and meanings (tonne, ton, tun) derive from the late Latin ''tunna'', "cask" - a full cask about a metre high could easily weigh a tonne. It may also be of Celtic origin.

Conversions

One tonne is equivalent to:

★ One megagram (exactly). Symbol Mg.

★
★ This is the official SI term, but not generally used in industry, in shipping nor ly.

★ 1000/0.45359237 pounds (exactly by definition), giving approximately

★
★ 2204.622 621 848 775 807 lb (to 19 significant digits)

★
★ 2204.622 622 lb (to ten significant digits)—an easy-to-remember figure

★
★ 2205 lb (rough but good enough for most calculations since loading (worst case) is usually the concern of interest)

★ 98.44% of a long ton

★
★ One long ton (2240 lb) is 101.605% of a tonne.

★ 110.25% of a short ton

★
★ One short ton (2000 lb) is 90.72% of a tonne

Explanation

The official symbol is 't'. 'T' and 'mT' and 'mt' (especially in the combination 'mmt' for "million metric tons" compare to Mt for megatonne) are also sometimes used, but all of these are deprecated since they conflict with internationally agreed SI symbols. T is the SI symbol for the tesla and m is SI prefix 'milli', meaning 1000th (though in practice fractional prefixes aren't generally used with the tonne). 'Te' is also sometimes used, particularly in the nuclear industry.
In France and the English-speaking countries that are predominantly metric, the spelling 'tonne' is widespread. However, in Britain, the ton used prior to metrication was the long ton of 2240 pounds (approximately 1016 kg). This is so close to the tonne that many people draw little distinction and continue to use the old spelling. For example, even the Guinness Book of World Records accepts metrication without marking this by changing the spelling. For the United States, 'metric ton' is the name for this unit used and recommended by NIST. [3] In the U.S. an unqualified mention of a "ton" almost invariably refers to a short ton of 2000 lb (about 907 kg).
Like grams and kilograms, tonnes gave rise to a (now obsolete) force unit of the same name: 1 tonne-force = 9.80665 kilonewtons (kN), a unit also often called simply "tonne" or "metric ton" without identifying it as a unit of force. Note that it is only the tonne as a unit of mass which is accepted for use with SI; the tonne-force or metric ton-force is not acceptable for use with SI.

Use of mass as proxy for energy

Main articles: TNT equivalent

The 'tonne of trinitrotoluene (TNT)' is used as a proxy for energy. Prefixes are also used e.g. kilotonne, megatonne, gigatonne; especially for expressing nuclear weapon yield, based on a specific combustion energy of TNT of 4.184 MJ/kg (or one calorie—specifically a ''thermochemical'' calorie—per milligram). Hence, 1 kt TNT = 4.184 TJ, 1 Mt TNT = 4.184 PJ.
The SI unit of energy is the joule. Assuming that TNT contains 1000 small (thermochemical) calories per gram (4.184 kJ/g), one tonne TNT is more correctly referred to as 4.184 gigajoules. It is usually used to describe the energy of explosions.

Metric ton in popular culture

★ ''Metric Ton'' is also the name of a hardcore band from Jacksonville, FL.

★ Fat Bastard (character) from the Austin Powers movies is introduced by Dr. Evil in saying that he weighs a metric ton.

★ In the Futurama episode A Flight to Remember it is discovered that Bender weighs a metric ton.

Derived units

'metric ton unit'

A metric ton unit (MTU) can mean 10 kg within metal (e.g. tungsten, manganese) trading, particularly within the USA. It traditionally referred to a metric ton of ore containing 1% (i.e. 10 kg) of metal.
http://www.emis.platts.com/thezone/guides/platts/metals/conversion.html
http://www.unc.edu/~rowlett/units/dictM.html
If the metal is uranium, the acronym 'MTU' is sometimes considered to be 'metric ton of uranium' i.e. 1000 kg (http://www-pub.iaea.org/MTCD/publications/PDF/rwmp-3/REFERENCE.pdf http://www.hanford.gov/rl/uploadfiles/ea/ea1319/ea1319.html, http://www.y12.doe.gov/library/acronyms/letter.php?index=M, http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0544/r4/ ).

See also

★ International System of Units ★ Metre-tonne-second system of units, a system of measurement that uses the tonne as a base unit ★ Units using the tonne ★ ★ ton of oil equivalent ★ ★ GTOE

★ Other tons ★ ★ short ton (S/T) ★ ★ long ton (L/T) ★ ★ tonnage ★ ★ ton (volume) ★ Conversion of units ★ Orders of magnitude (mass)

References

★ NIST Special Publication 811, ''Guide for the Use of the International System of Units (SI)''
1. Section 4.1 of The International System of Units (SI), 8th Edition, 2006
2. Act of July 28, 1866, codified in 15 U.S.C. §205 [1]
3. "Metric System of Measurement: Interpretation of the International System of Units for the United States", Federal Register notice of July 28, 1998, 63 F.R. 40333 [2]
4. http://www.bipm.org/en/CIPM/db/1967/2/

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