A long ton is the name used in the US for the unit called the "ton" in the avoirdupois or Imperial system of measurements, as used (alongside the metric system) in the United Kingdom and to some extent in other Commonwealth countries. It is equal to 2240 pounds (approximately 1016 kilograms). It has some limited use in the US, most commonly in measuring the displacement of ships.
The standard ton in the US measurement system is the "short ton", equal to 2000 pounds (approximately 907.2 kg). Both long and short tons are defined as 20 hundredweights, but a hundredweight is 112 pounds (which is equal to 8 stone) in the Imperial system and 100 pounds in the US system.
The spelling "tonne" denotes the metric tonne of 1000 kilograms (approximately 2204.6 pounds).
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