Long ton, also known as the imperial ton or displacement ton, is the name for the unit called the "ton" in the avoirdupois system of weights or Imperial system of measurements. It was standardised in the thirteenth century and is used in the United Kingdom and several other British Commonwealth of Nations countries alongside the mass-based metric tonne defined in 1799.
|Unit system||Imperial units, U.S. customary units|
|In base units||2,240 lb|
|1 in ...||... is equal to ...|
|SI base units||1,016.047 kg|
|Metric tons||1.016047 t|
|Short tons||1.12 short tons (exactly)|
A long ton is defined as exactly 2,240 pounds. The long ton arises from the traditional British measurement system: A long ton is 20 hundredweight (cwt), each of which is 8 stone (1 stone = 14 pounds). Thus a long ton is 20 × 8 × 14 lb = 2,240 lb.
- 2,240 pounds or 1,016 kilograms or 1.016 metric tons
- 12% more than the 2,000 pounds of the North American short ton
- the weight of 35 cubic feet (0.99 m3) of salt water with a density of 64 pounds per cubic foot (1.03 g/cm3)
It has some limited use in the United States, most commonly in measuring the displacement of ships, the volume-to-carrying-weight of fuels and in trade of baled commodities and bulk goods like elemental sulfur. The long ton was the unit prescribed for warships by the Washington Naval Treaty of 1922—for example battleships were limited to a displacement of 35,000 long tons (36,000 t; 39,000 short tons).
To comply with the practices of the European Union, the British Imperial ton was explicitly excluded from use for trade by the United Kingdom's Weights and Measures Act of 1985.
The long ton remains in informal use by some heritage rail companies and remains on a limited number of weight limit signs on roads (usually in remote areas away from major towns and cities where tonnes are used).
- "Definitions, Tonnages and Equivalents". Military Sealift Fleet Support Command Ships. Archived from the original on 25 May 2017. Retrieved 11 September 2016.
- Dictionary.com - "a unit for measuring the displacement of a vessel, equal to a long ton of 2240 pounds (1016 kg) or 35 cu. ft. (1 cu. m) of seawater."
- legislation.gov.uk: Weights and Measures Act 1985 Retrieved 17 January 2013.
- A Dictionary of Weights, Measures, and Units, edited by Donald Fenna, Oxford University Press