Long ton, also known as the
imperial ton or
weight ton, is the name for the unit called the "
ton" in the
avoirdupois or
Imperial system of measurements standardised in the thirteenth century that is used in the
United Kingdom and several other
Commonwealth countries alongside the French
metrication invented in 1799. One long ton is equal to 2,240 pounds (1,016 kg), 12% larger than a
short ton and 1.6% larger than the 1,000-kilogram (2,205 lb)
tonne, or 35 cubic feet (0.9911 m
3) of salt water with a density of 64 lb/cu ft (1.025 g/ml). It has some limited use in the United States, most commonly in measuring the
displacement of
ships, and in trade of elemental sulfur, and was the unit prescribed for
warships by the
Washington Naval Treaty 1922—for example
battleships were limited to a displacement of 35,000 long tons (36,000 t; 39,000 short tons).