Tonne
For the units of mass, force, and other quantities in general, see Ton.A
tonne (symbol 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. 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.
1 tonne is defined as
1000 kilograms or
1 megagram.
| Multiple | Name | Symbol | | Multiple | Name | Symbol | | 100 | tonne | | | |
| 101 | decatonne | 10â€"1 | decitonne | dt |
| 102 | hectotonne | 10â€"2 | centitonne | ct |
| 103 | kilotonne | 10â€"3 | millitonne | mt |
| 106 | megatonne | 10â€"6 | microtonne | µt |
| 109 | gigatonne | 10â€"9 | nanotonne | nt |
| 1012 | teratonne | 10â€"12 | picotonne | pt |
| 1015 | petatonne | 10â€"15 | femtotonne | ft |
| 1018 | exatonne | 10â€"18 | attotonne | at |
| 1021 | zettatonne | 10â€"21 | zeptotonne | zt |
| 1024 | yottatonne | 10â€"24 | yoctotonne | yt |
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.
One tonne is equivalent to:
* 1 megagram (exactly). Symbol Mg. This is the SI term
* 1000/0.45359237 pounds (exactly) ~ 2205 pounds
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. [
1] In the US 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.
M is SI standard for millon or 1e6 and Metric tonne being t, this would make millon metric tonnes as Mt in SI nomenclature.
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.
* Units using the tonne
**
ton of oil equivalent**
GTOE* Other
tons
**
short ton**
long ton**
tonnage**
ton (volume)*
Conversion of units*
Orders of magnitude (mass)*NIST Special Publication 811,
Guide for the Use of the International System of Units (SI)
