Tonne

This article is about the metric tonne. For the imperial ton, see Ton.

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 or 1 megagram. It is not an SI unit but is accepted for use with the SI. The proper SI unit is the megagram. 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 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.

Definition

1 tonne is defined as 1000 kilograms or 1 megagram.

Multiples

Multiple	Name	Symbol		Multiple	Name	Symbol
100	tonne	t
101	decatonne	dat		10–1	decitonne	dt
102	hectotonne	ht		10–2	centitonne	ct
103	kilotonne	kt		10–3	millitonne	mt
106	megatonne	Mt		10–6	microtonne	µt
109	gigatonne	Gt		10–9	nanotonne	nt
1012	teratonne	Tt		10–12	picotonne	pt
1015	petatonne	Pt		10–15	femtotonne	ft
1018	exatonne	Et		10–18	attotonne	at
1021	zettatonne	Zt		10–21	zeptotonne	zt
1024	yottatonne	Yt		10–24	yoctotonne	yt

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:

• 1 megagram (exactly). Symbol Mg. This is the SI term
• 1000/0.45359237 pounds (exactly) ~ 2205 pounds (by comparison the imperial measurements long ton and short ton are 2240 and 2000 pounds, respectively)

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).

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.

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Metric ton in popular culture

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

See also

• 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)

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