Grain (measure)

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A grain (symbol: gr) is a unit of mass now equal to exactly 64.79891 milligrams, in all English mass and weight systems (avoirdupois, Apothecaries’ and troy).

An avoirdupois pound is 7,000 grains, whereas a troy pound is 5,760 grains. There have been other English pounds with round sizes in grains.

A metric or pearl grain is equal to 50 milligrams or ¹⁄₄ of a carat as used in pearl and diamond nomenclature.

Originally, a grain was the weight of a grain seed from the middle of an ear of barley; 64 wheat berries were set to weigh as much as 45 barleycorns (i.e., a wheat kernel was conventionally considered to be ⁴⁵⁄₆₄ of the grain used as a unit of mass). (A barleycorn was also ¹⁄₃ inch as a unit of length).

[edit] Usage

Grains are still used as a measure for older drugs such as aspirin, though the milligram has almost completely replaced them. Grains are currently used in the United States and Canada <ref name= Canadian Ammo>Marstar Canada: Ammunition and Reloading Supplies (English). Retrieved on Sept 21st, 2006.</ref> to measure the mass of bullets and gunpowder, and scales for handloading measure in grains; bullets are generally measured in increments of 1 grain, gunpowder in increments of 0.1 grains. Grains are used to measure arrows, and arrow parts <ref name= Canadian Arrows>Canadian Tire en ligne : Magasiner au Canada (French/Français). Retrieved on Sept 21, 2006.</ref> in archery. Grains are also used in environmental permitting to quantify particulate emissions.