Conversion from 100 Grains to Long tons

Information about the Grain (gr)

The grain is a unit of mass equal to exactly 64.79891 milligrams. Its symbol is gr. It is the smallest unit in the imperial and US customary systems, and the only one shared identically by the avoirdupois, troy and apothecaries systems, which makes it the hinge on which conversions between them turn.

Its origin is agricultural and literal: a grain of barley, or in some traditions wheat, taken as a natural standard because seeds from a single crop are remarkably uniform. The English statute of 1266 defined the penny as the weight of thirty-two wheat grains taken from the middle of the ear. That definition survived in principle until the nineteenth century, when the grain was fixed by law against the pound rather than against any seed. Seven thousand grains make an avoirdupois pound, and 5760 make a troy pound.

Firearms are where the unit is most alive today. Bullet mass is quoted in grains almost universally, so a 55-grain rifle bullet or a 230-grain pistol bullet is standard language among shooters worldwide, including in metric countries. Propellant charges are weighed in grains as well, and reloading scales are calibrated in them.

Pharmacy used the grain for centuries, and the five-grain aspirin tablet is the ancestor of today's 325-milligram tablet, a figure that looks arbitrary in metric units and obvious in the old ones. Dentistry, arrow and archery components, and the pearl and gemstone trades all retain it in places.

Its most remarkable property is that it is the same in every English weight system. Troy, avoirdupois and apothecaries' weights each divide differently above the grain — a troy pound is 5760 grains and an avoirdupois pound 7000 — but all three rest on the identical grain of 64.79891 milligrams. That made the grain the common currency by which a goldsmith's weights and a grocer's weights could be compared, and it is the reason the unit survived standardisation while its larger relatives were pruned away. Handloaders exploit the same precision today: powder charges are weighed to a tenth of a grain, about six milligrams, because a small error in charge produces a large change in pressure.

One grain equals 64.79891 milligrams exactly, one seven-thousandth of an avoirdupois pound, or about 0.002286 ounces.

Information about the Long ton (t)

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.