Tonne Totally Explained

A tonne (t) or metric ton (M/T), also referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms. It isn't an SI unit but is accepted for use with the SI. 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's 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 as a millier or a tonneau. However, neither of these are in use and though they still appear in the statute, they've been declared obsolete by NIST.

Definition

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

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.

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. (External Link

) 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's only the tonne as a unit of mass which is accepted for use with SI; the tonne-force or metric ton-force isn't acceptable for use with SI.

Use of mass as proxy for energy

The tonne of trinitrotoluene (TNT) is used as a proxy for energy. Prefixes are also used for example 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's discovered that Bender weighs a metric ton.

Derived units

metric ton unit
A metric ton unit (MTU) can mean 10 kg within metal (for example tungsten, manganese) trading, particularly within the USA. It traditionally referred to a metric ton of ore containing 1% (for example 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' for example 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/ ).

External results

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