| Long tons (t) | Ounces (oz) |
|---|---|
| 1 Long ton | 35840 oz |
| 2 Long tons | 71680 oz |
| 3 Long tons | 107520 oz |
| 4 Long tons | 143360 oz |
| 5 Long tons | 179200 oz |
| 10 Long tons | 358400 oz |
| 20 Long tons | 716800 oz |
| 25 Long tons | 896000 oz |
| 50 Long tons | 1792000 oz |
| 100 Long tons | 3584000 oz |
| Reference | Long tons (t) | Ounces (oz) |
|---|---|---|
| A sheet of A4 paper (80 gsm) | 0.00000492103 t | 0.17637 oz |
| One litre of water | 0.000984207 t | 35.274 oz |
| Average adult human | 0.0688945 t | 2469.18 oz |
| A small car | 1.37789 t | 49383.5 oz |
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.
The ounce is a unit of mass equal to one sixteenth of an avoirdupois pound, or exactly 28.349523125 grams. Its symbol is oz, from the Italian onza. It is the everyday small weight of the United States and remains in common use in the United Kingdom alongside metric units.
There are several ounces, and confusing them is easy. The avoirdupois ounce described here is the one used for food and general goods. The troy ounce, used for gold, silver and platinum, is about 31.103 grams, some ten per cent heavier, which is why a troy pound of twelve ounces weighs less than an avoirdupois pound of sixteen. The fluid ounce is not a mass at all but a volume, and the imperial and US fluid ounces differ from each other by about four per cent.
American food packaging is built on the ounce. Net weights appear in ounces below sixteen and in pounds and ounces above, and recipe quantities for cheese, chocolate, pasta and meat are given the same way. Postal rates for letters step in ounces, and boxing, wrestling and other weight-class sports state limits in pounds and ounces.
The word comes from the Latin uncia, meaning a twelfth part, which is also the ancestor of the inch. That original twelfth survives in the troy ounce but not in the avoirdupois one, whose sixteenth-of-a-pound relationship came later from the wool trade of medieval Europe. Two units with the same name and different arithmetic is the direct result.
Precious metals are the other ounce's territory. Gold, silver, platinum and palladium are priced per troy ounce of 31.1035 grams, about ten per cent heavier than the avoirdupois ounce used for groceries, and every quoted bullion price in the world refers to it. A one-ounce gold coin is therefore heavier than an ounce of butter, and a bar described as a kilogram contains 32.15 troy ounces rather than 35.27 ordinary ones. The troy system also keeps its own subdivisions, with 20 pennyweights to the ounce, which is why a jeweller's scale and a kitchen scale are calibrated differently even when both are marked in ounces.
One ounce equals 28.349523125 grams exactly, one sixteenth of a pound, or 437.5 grains.