Ton

Ton is any of several units of measure of mass, volume or force. It has a long history and has acquired several meanings and uses.

As a unit of mass, ton can mean:

• the long ton, which is Template:Convert
• the tonne, also called the metric ton, which is Template:Convert) or 1 megagram.
• the short ton, which is Template:Convert

Its original use as a unit of volume has continued in the capacity of cargo ships and in units such as the freight ton and a number of other units, ranging from Template:Convert in size.

Because the ton (of any system of measuring weight) is usually the heaviest unit named in colloquial speech, its name also has figurative uses, singular and plural, informally meaning a large amount or quantity, or to a great degree, as in "There's a ton of bees in this hive," "We have tons of homework," and "I love you a ton."

History

The ton is derived from the tun, the term applied to a cask of the largest capacity. This could contain a volume between Template:Convert, which could weigh around Template:Convert, and occupy some Template:Convert of cargo space.<ref name=BTS.GOV>{{#invoke:citation/CS1|citation |CitationClass=web }}. "Historically, a very important and standard cargo for European sailing vessels was wine, stored and shipped in casks called tuns. These tuns of wine, because of their uniform size and their universal demand, became a standard by which a ship's capacity could be measured. A tun of wine weighed approximately 2,240 pounds, and occupied nearly 60 cubic feet." (Gillmer, Thomas (1975). Modern Ship Design. United States Naval Institute.) "Today the ship designers standard of weight is the long ton which is equal to 2,240 pounds." This is the weight of 35 cubic feet of Sea Water at a specific gravity of 1.025, compared to Fresh Water, specific gravity of 1.000 usually measured at 60 degrees F. Handy numbers: 35, 36, 37, number of Cubic Feet per Salt Water, Fresh Water and Lube Oil.</ref>

Units of mass/weight

There are several similar units of mass or volume called the ton:

Full name(s)	Common name	QuantityTemplate:Efn	Symbol	Notes
long ton<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>	"ton" (United Kingdom)	Template:Convert	LT	Used in Ireland and Commonwealth countries that formerly used, or still use the Imperial system
short ton<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>	"ton" (United States)	Template:Convert	tn<ref name=NIST44-C> {{#invoke:citation/CS1|citation	CitationClass=web }}</ref> or st<ref> {{#invoke:citation/CS1|citation	CitationClass=web }}</ref>	Used in the United States and in some industries in Canada
tonne<ref name="si2019">Template:SIbrochure9th</ref> (equivalent to one megagram)	"tonne"; "metric ton"	1,000 kg (about 2,204.6226 lb)	t<ref name="si2019">Template:SIbrochure9th</ref>	Defined in the International System of Units. Used worldwide.
shortweight tonTemplate:Refn		2,240 lb		Used in the iron industry in the 17th and 18th centuries.
longweight ton<ref name="longshortweight" group="lower-alpha"/>		2,400 lbTemplate:Refn

The difference between the short ton and the other common forms ("long" and "metric") is about 10%, while the metric and long tons differ by less than 2%.

The metric tonne is usually distinguished by its spelling when written, but in the United States and United Kingdom, it is pronounced the same as ton, hence is often spoken as "metric ton" when it is necessary to make the distinction. In the United Kingdom the final "e" of "tonne" can also be pronounced (Template:IPAc-en).<ref name="oedtonne">Template:Cite OED</ref> In Australia, it is pronounced Template:IPAc-en.

In Ireland and most members of the Commonwealth of Nations, a ton is defined as Template:Convert.Template:Efn<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

In the United States and Canada,<ref name=Canada>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> a ton is defined as Template:Convert.

Other units of mass/weight

• Deadweight ton (abbreviation 'DWT' or 'dwt') is a measure of a ship's carrying capacity, including bunker oil, fresh water, ballast water, crew, and provisions. It is expressed in tonnes (Template:Convert) or long tons (Template:Convert). This measurement is also used in the U.S. tonnage of naval ships.
• Increasingly, tonnes are being used rather than long tons in measuring the displacement of ships.
• Harbour ton, used in South Africa in the 20th century, was equivalent to (Template:Convert) or 1 short ton.

Template:Anchor Assay ton (abbreviation 'AT') is not a unit of measurement but a standard quantity used in assaying ores of precious metals. A short assay ton is approximately Template:Convert and a long assay ton is approximately Template:Convert.<ref>Template:Cite book</ref>Template:Citation needed These amounts bear the same ratio to a milligram as a short or long ton bears to a troy ounce. Therefore, the number of milligrams of a particular metal found in a sample weighing one assay ton gives the number of troy ounces of metal contained in a ton of ore.

In documents that predate 1960 the word ton is sometimes spelled tonne,Template:Citation needed but in more recent documents tonne refers exclusively to the metric ton.

In nuclear power plants tHM and MTHM mean tonnes of heavy metals, and MTU means tonnes of uranium. In the steel industry, the abbreviation THM means 'tons/tonnes hot metal', which refers to the amount of liquid iron or steel that is produced, particularly in the context of blast furnace production or specific consumption.

Subdivisions

Both the UK definition of long ton and US definition of short ton have similar underlying bases. Each is equivalent to 20 hundredweight; however, they are long Template:Convert or short hundredweight Template:Convert, respectively.

Before the 20th century there were several definitions. Prior to the 15th century in England, the ton was 20 hundredweight, each of 108 lb, giving a ton of Template:Convert.Template:Citation needed In the 19th century in different parts of Britain, definitions of 2,240, or 2,352, or 2,400 lb were used, with 2,000 lb for explosives; the legal ton was usually 2,240 lb.<ref>Definitions of 2,000, 2,240, 2,352, and 2,400 lb are included in citations listed in the Oxford English Dictionary, 2nd ed. OED cites an 1858 dictionary of trade products "the legal ton by weight is usually 20 cwt".</ref>

In the United Kingdom, Canada, Australia, and other areas that had used the imperial system, the tonne is the form of ton legal in trade.

Units of volume

Template:See also The displacement, essentially the weight, of a ship is traditionally expressed in long tons.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> To simplify measurement it is determined by measuring the volume, rather than weight, of water displaced, and calculating the weight from the volume and density.<ref>Displacement ton Dictionary of international trade retrieved 22July2010</ref> For practical purposes the displacement ton (DT) is a unit of volume, Template:Convert, the approximate volume occupied by one ton of seawater (the actual volume varies with salinity and temperature).<ref>A Dictionary of Weights, Measures, and Units, Donald Fenna, 2002 Template:ISBN</ref> It is slightly less than the 224 imperial gallons (1.018 m³) of the water ton (based on distilled water).

One measurement ton or freight ton is equal to Template:Convert, but historically it has had several different definitions. It is used to determine the amount of money to be charged in loading, unloading, or carrying different sorts of cargo. In general if a cargo is heavier than salt water, the actual weight is used. If it is lighter than salt water, e.g. feathers, freight is calculated in measurement tons of 40 cubic feet.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Gross tonnage and net tonnage are volumetric measures of the cargo-carrying capacity of a ship.

The Panama Canal/Universal Measurement System (PC/UMS) is based on net tonnage, modified for Panama Canal billing purposes. PC/UMS is based on a mathematical formula to calculate a vessel's total volume; a PC/UMS net ton is equivalent to 100 cubic feet of capacity.<ref>Panama Canal Tolls Template:Webarchive, Panama Canal Authority. Retrieved 10 May 2006.</ref>

The water ton is used chiefly in Great Britain, in statistics dealing with petroleum products, and is defined as Template:Convert,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> the volume occupied by Template:Convert of water under the conditions that define the imperial gallon.

Colloquial English

• Ton is also used informally, often as slang, to mean a large amount of something.<ref>Merriam-Webster's English Dictionary defines ton as: "a great quantity". [1]</ref>
• In Britain, a ton is colloquially used to refer to 100 of a given unit. Ton can thus refer to a speed of 100 miles per hour, and is prefixed by an indefinite article, e.g. "Lee was doing a ton down the motorway"; to money e.g. "How much did you pay for that?" "A ton" (£100); to 100 points in a game e.g. "Eric just threw a ton in our darts game" (in some games, e.g. cricket, more commonly called a century); or to a hundred of any other countable figure.<ref>Colin R. Chapman, Weights, Money and Other Measures Used by our Ancestors, p.93, Genealogical Publishing Com, 1996 Template:ISBN.</ref><ref>Template:Cite book</ref><ref>The Oxford English Dictionary 2nd ed. lists colloquial use of "ton" from 1946 for £100, and later 100 mph, and for 100 in general.</ref>

See also

• Conversion of units

• English units
• Gross ton mile
• Imperial units
• Systems of measurement
• TNT equivalent
• Ton of refrigeration
• truck classification
• unit of energy
• United States customary units