The long ton is a unit of mass equal to 2240 pounds, or about 1016.047 kilograms. It is the ton of the British imperial system, sometimes called the imperial ton or the gross ton, and it sits within one and a half per cent of the metric tonne, which is both convenient and a persistent source of error.
Three tons compete for the same word. The long ton is 2240 pounds, the short or American ton is 2000 pounds, and the tonne is 1000 kilograms, roughly 2204.6 pounds. The long ton and the tonne differ by about sixteen kilograms, small enough to be invisible in a rough estimate and large enough to matter across a shipload. Contracts, customs declarations and commodity quotations therefore name the ton explicitly rather than relying on context.
Its structure follows the rest of the imperial system: twenty hundredweight of 112 pounds each. That is where the 2240 comes from, and it makes the long ton the natural top of a chain running pound, stone, hundredweight, ton, each step a whole number of the last.
British shipping, mining and steel used it for well over a century, and it survives in some maritime contexts and in older engineering literature. The displacement of warships is still often quoted in long tons, which is why published figures for historic vessels can differ by a couple of per cent depending on which ton the source used.
Shipping complicates the word further by using ton for things that are not masses at all. A register ton is a hundred cubic feet of enclosed space, used to size a vessel for harbour dues; a freight ton may be a mass or a volume, whichever yields the larger charge; and displacement, the figure by which warships are described, is the mass of water a hull pushes aside, historically stated in long tons. Reading a ship's particulars therefore means checking which ton is meant before comparing anything. Deadweight tonnage, the cargo, fuel and stores a ship can carry, is a mass and is now given in metric tonnes, but older registers state it in long tons.
One long ton equals 2240 pounds, about 1016.047 kilograms, or 1.12 short tons.
| Unit | Symbol | 1 Long ton equals | 1 of these equals | Converter |
|---|---|---|---|---|
| Nanogram | ng | 1.0160469088 × 1015 ng | 9.84206527611 × 10-16 t | Long tons to Nanograms |
| Microgram | μg | 1016046908800 μg | 9.84206527611 × 10-13 t | Long tons to Micrograms |
| Milligram | mg | 1016046908.8 mg | 9.84206527611 × 10-10 t | Long tons to Milligrams |
| Gram | g | 1016046.9088 g | 0.000000984206527611 t | Long tons to Grams |
| Kilogram | kg | 1016.0469088 kg | 0.000984206527611 t | Long tons to Kilograms |
| Tonne | t | 1.0160469088 t | 0.984206527611 t | Long tons to Tonnes |
| Grain | gr | 15680000 gr | 0.0000000637755102041 t | Long tons to Grains |
| Dram | dr | 573440 dr | 0.00000174386160714 t | Long tons to Drams |
| Ounce | oz | 35840 oz | 0.0000279017857143 t | Long tons to Ounces |
| Pound | lb | 2240 lb | 0.000446428571429 t | Long tons to Pounds |
| Stone | st | 160 st | 0.00625 t | Long tons to Stones |
| Hundredweight | cwt | 20 cwt | 0.05 t | Long tons to Hundredweights |