The word ton or tonne is derived from the Old English ''tunne'', and ultimately from the Old French language ''tonne'', and referred originally to a large cask with a volume of 252 wine gallons, which holds approximately 2100 pounds of water. Such a barrel (of any similar volume) is still called a tun in British English, but this usage is dying out.
The modern spelling ''tonne'', almost always referring to the ''metric ton'' of 1000 kilograms (or the associated obsolete force unit) when used in English, is a direct borrowing from the French language.
There are a ''ton'' of tons:
==Units of mass==
There are three similar units of mass called the ton or tonne:
* tonne or metric ton = 1 E3 kg (~2204.62 Pound). The official symbol is t, but mT, MT, and T are also used. This is not an SI unit, though it is acceptable for use with SI. The name for this unit in SI is the megagram (symbol: Mg).
* short ton (or simply ton in the United States) = 2000 lb (exactly 1 E2 kg).
* long ton (or weight ton or gross ton, or simply ton in the United Kingdom) = 2240 lb (exactly 1 E3 kg), is an avoirdupois unit commonly used in the United Kingdom and still common in British areas of influence. The UK now often uses the metric (1000 kg) tonne which it is conveniently very similar to —less than 2% difference.
The long ton is used for petroleum products. It is also used in the U.S., as in many other countries, for things such as the deadweight tonnage of naval ships.
* As a displacement ton the long ton is normally measured as the mass of 35 cubic feet of sea water. Increasingly, metric tons are being used rather than long tons in measuring the displacement of ships. ''See'' tonnage.
**Deadweight ton (abbreviation 'dwt') for the capacity of a ship in the number of long tons (2240 pounds).
**Harbour ton used in South Africa in the 20th century, equal to 2000 pounds or one short ton.
Both the short ton and the long ton are composed of twenty hundredweights, each having different values for the hundredweight (100 and 112 pounds respectively). Prior to the 15th century in England, the ton was composed of twenty hundredweights, each of 108 lb, giving a ton of 2160 pounds.
In the context of nuclear power plants, tHM and MTHM mean (metric) tons of Heavy metals, and MTU means metric tons of uranium.
Assay ton (abbreviation 'AT') is not a unit of measurement (nobody ever has ''x'' assay tons of something), but rather a standard quantity used in assaying ores of precious metals; it is 29 1/6 grams (short assay ton) or 32 2/3 grams (long assay ton), the amount which bears the same ratio to a milligram as a short/long ton bears to a troy ounce. In other words, the number of milligrams of a particular metal found in a sample of this size gives the number of troy ounces contained in a short/long ton of ore.
==Units of force==
There are also the units of force based on each of these three mass units. However, it is only the metric ton or tonne as a unit of mass which is acceptable for use with SI. The metric tonne force (tonne force), like the kilogram force, is ''not'' acceptable for use with SI.
*1 short ton force = 2000 pound-force = 8.896443230521 kilonewtons (kN)
*1 long ton force = 2240 lbf = 9.96401641818352 kN
*1 metric ton force = 1000 kilogram-force = 9.80665 kN
==Units of volume==
''See also'' ton (volume), tonnage.
The freight ton or measurement ton is a unit of volume used for describing ship capacities (tonnage) or cargo. One measurement ton is equal to:
* 40 cubic foot
* 1.481(481) cubic yards (the "481" digit sequence repeats infinitely)
* 1,132.67386368 litres
* 1.13267386368 cubic metres
The amount of ''fresh water'' at 4C displaced by one measurement ton has a mass similar to the ton masses listed above: about 1133 kg or 2497 lb. The measurement ton is abbreviated as M/T, MT, or MTON, which can cause it to be confused with the tonne.
The register ton is also a unit of volume used for the cargo capacity of a ship, defined as 100 cubic feet (roughly 2.83 cubic metres). It is often abbreviated GRT for gross registered ton. It is known as a ''tonneau de mer'' in Belgium, but, in France, a ''tonneau de mer'' is 1.44 cubic metres or about 1.88 cubic yards.
The Panama Canal net ton, a unit of volume used for billing for ships going through the Panama Canal, the the same as the register ton. The fee for example in the 1990s was roughly a couple USD for each unit.
The water ton was formerly used in Great Britain and equal to 224 imperial gallons (the volume occupied by a mass of one long ton under the conditions which define the imperial gallon).
See 1 E-1 m and orders of magnitude (volume) for a comparison with other volumes.
==Units of energy and power==
*In refrigeration and air-conditioning, a refrigeration ton can be:
**The power required to cool 1 short ton of water by 1 Fahrenheit every 10 minutes = 12,000 BTU/h = 3,516.85284 watts)
**The power required to cool 1 long ton of water by 1 Fahrenheit every 10 minutes = 13,440 BTU/h = 3,938.87518 watts
**A corresponding unit of energy equal to that power for a period of a day, or 24 × 12,000 BTU = 288,000 Btu = 303,856,086 joules
*A ton of TNT or ''tonne of TNT'' is equal to 1,000,000 grams (1 metric tonne) at a conventional energy value of 1000 small (thermochemical) calories per gram, thus 1 calorie, or 4.184 gigajoules. ''See also'' megaton.
*A ton of coal equivalent or ''tonne of coal equivalent'' (TCE), a conventional value of 7 Gcal (IT) = 29.3076 GJ.
*A ton of oil equivalent or ''tonne of oil equivalent'' (TOE), a conventional value of 10 Gcal (IT) = 41.868 GJ. ''See also'' GTOE.
==Miscellaneous tons==
*Ton is also used informally to mean a large amount of something.
*Units of speed: in slang or informal usage, a ton can be
**100 mi/h
**100 km/h
*In money, a ''ton'' is slang for 100 GBP (pounds sterling) —this is primarily used in London, England.
*In darts, a ''ton'' (or ''ton up'') is a score of 100 or more points with three darts.
*In motor vehicles, many trucks are classified into groups loosely related to their carrying capacity as 1/2 ton, 3/4 ton, 2 1/2 ton (''deuce-and-a-half'' in U.S. military slang), 5 ton, etc.
==See also==
*Conversion of units
*Medieval weights and measures
*Ancient weights and measures
== External links ==
* [http://www.ex.ac.uk/trol/scol/ccvol.htm Conversion calculator for units of mass (Cleave Books)]
Units of massUnits of volumeCustomary units in the United StatesImperial units
Ton
Kilograms abbreviation is Kg with capital K, because is a multiplier, and multpliers in the International system are in capitals.
:Wrong. -- User:The Anome 16:48 14 Jul 2003 (UTC)
SI_prefix's the list of SI prefixes. User:Euyyn 12:05, 31 Aug 2004 (UTC)
Is the volume ton 252 US or imperial gallons? User:Jasonq 17:29, 27 Oct 2004 (UTC)
==Gene Nygaard's [http://www.armedforces.co.uk/navy/listings/l0001.html]==
Gene, what's that supposed to link to? The page currently lists some statistics about the fleet, including tonnage. What's that got to do with the imperial ton (of mass) going out? Please explain, as I'm confused.
User:Urhixidur 17:54, 2005 Apr 28 (UTC)
:Those are long tons (1016 kg), same as those used in the United States for the same purpose. They are not metric tons, and those long tons are not just "formerly" used, but "currently" used. User:Gene Nygaard 18:02, 28 Apr 2005 (UTC)
:: Current but only in a small area (naval), eg the whole of agriculture and food production works in metric tons. Building works are in metric. User:GraemeLeggett 08:08, 29 Apr 2005 (UTC)
== Accuracy/Overaccuracy ==
Isn't the number of significant figures rather overstated? Might I suggest 2 or three decimal places tops. User:GraemeLeggett 12:33, 25 May 2005 (UTC)
:Anybody can round, so it is better to provide exact conversions whenever possible.
:User:Urhixidur 03:14, 2005 May 26 (UTC)
::There is no official definition of a short ton force or a long ton force (there is for the metric ton force, a unit no more acceptable for use with SI than the English tons force). That's because there is no official definition of a pound force. We often borrow the acceleration which is official for defining kilograms force to define pounds force, but other accelerations such as 32.16 ft/s are used for this purpose as well. User:Gene Nygaard 04:28, 26 May 2005 (UTC)
::: It seems to me then that the high accuracy numbers should be collected together towards the end in a table, not in the main text User:GraemeLeggett 08:44, 26 May 2005 (UTC)
See other meanings of words starting from letter: