# Ton

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The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.

It is derived from the tun, the term applied to a barrel of the largest size. This could contain a volume between 210 and 256 gallons, which could weigh around 2,000 pounds and occupy some 60 cubic feet of space.[1]

In the United Kingdom, the ton is a unit of measure which, when it ceased to be legal for trade in 1985, was defined in British legislation as being a weight or mass equal to 2,240 pounds (1,016 kg) (avoirdupois pounds).[2] In the United States and Canada,[3][not in citation given] however, a ton is defined to be 2,000 pounds (907 kg). To avoid confusion, the former is more specifically referred to as a "long ton" and the latter, a "short ton"; neither should be confused with the metric ton (tonne), which is 1,000 kilograms (2,205 lb). While they do vary, a ton is generally one of the heaviest units of weight or mass referred to in colloquial speech.

The term "ton" is also used to refer to a number of units of volume, ranging from 35 to 100 cu ft in capacity.

It can also be used as a unit of energy, expressed as an equivalent of coal burnt, TNT detonated, or in refrigeration, ice melted.

## Contents

### Units of mass/weight

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

• The long ton is used for petroleum products such as aviation fuel.
• 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 (1000 kg) or long tons (2240 pounds, about 1016 kg). 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. See tonnage.
• Harbour ton used in South Africa in the 20th century, 2000 pounds or one short ton.