|Unit system||Imperial units, U.S. customary units|
|In base units||2,240 lb|
|SI base units||1,016.047 kg|
|Metric tons||1.016047 t|
|Short tons||1.12 short tons (exactly)|
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.
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:
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).
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).