Long ton, also known as the imperial ton or displacement ton, is the name for the unit called the "ton" in the avoirdupois 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.
It is not to be confused with the short ton a unit of weight equal to 2,000 pounds (907.18474 kg) used in the United States and in Canada before metrication also referred to simply as a "ton".
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.
A long ton, also called the weight ton (W/T), imperial ton, or displacement ton, is equal to:
- 2,240 pounds (1,016 kg)
- 12% more than the 2,000 pounds of the North American short ton
- approximately 1.0160 tonnes (metric tons)
- 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.
- Short ton, equal to 2,000 lb (907.2 kg).
- Tonnage, volume measurement used in maritime shipping, originally based on 100 cubic feet (2.83 m3).
- Tonne, also known as a metric ton (t), equal to 1,000 kg (2,205 lb) or 1 megagram.
- ^ a b c d e "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
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