Long ton (L/T sometimes known as a gross ton, weight ton, or imperial ton) is the name for the unit called the "ton" in the avoirdupois or Imperial system of measurements, as formerly used in the United Kingdom and several other Commonwealth countries. It has been mostly replaced by the short ton in the United States and the metric tonne elsewhere. It is equal to 2240 pounds (1016.0469088 kilograms). It has some limited use in the United States, most commonly in measuring the displacement of ships, and was the unit prescribed for warships (e.g., battleships limited to 35,000 tons) in the international agreements between the world wars.
The standard ton in the U.S. measurement system is the "short ton", equal to 2000 pounds (exactly 907.18474 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 (long or gross hundredweight) and 100 pounds in the U.S. system (short or net hundredweight).
The spelling "tonne" denotes the metric tonne of 1000 kilograms (approximately 2204.623 pounds).