Tonne Tonne Tissue Category="Units of mass"A tonne, sometimes known as metric ton in American English, (symbol t) is a unit of Mass. It is not an SI unit but is accepted for use with the SI. The SI unit of mass is the Kilogram and a tonne is correctly described in SI as a megagram.

Definition

1 t = 1000 kg

Multiples

Multiple	Name	Symbol
10⁰	tonne	t
10³	kilotonne	kt
10⁶	megatonne	Mt
10⁹	gigatonne	Gt
10¹²	teratonne	Tt
10¹⁵	petatonne	Pt
10¹⁸	exatonne	Et
10²¹	zettatonne	Zt
10²⁴	yottatonne	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 late latin tunna (cask). It may be of celtic origin. A full cask about a metre high could easily weigh 1 tonne.

Conversions

One tonne is equivalent to:

1 megagram (exactly). Symbol Mg. This is the SI term
2204.62262 pounds

Explanation

The official symbol is t, but T and mT and mt (especially in the combination mmt for "million metric tons") are also used.

In France and the English-speaking countries that are predominately metric, the spelling tonne is widespread. However, in Britain, the common people consider that its measure is very close to that of the Long ton and often don't bother with the distinctive spelling; for example, even the Guiness Book of World Records accepts metrification without marking this by changing the spelling. For the United States, metric ton is the name for this unit used and recommended by NIST.

Like grams and kilograms, tonnes have also given rise to a 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.

The ton of TNT or tonne of Trinitrotoluene is a unit of energy with the tonne as a proxy term. This unit is not acceptable for use with SI. Assuming 1000 small (thermochemical) calories per gram (4.184 kJ/g) and thus a tonne of TNT is 4.184 GJ.

References