Grain

A grain is a unit of measurement of mass that is based upon the mass of a single seed of a typical cereal. Historically, in Europe, the average masses of wheat and barley grain were used to define units of mass. Since 1958, the grain or troy grain (Symbol: gr) measure has been redefined on the basis of the unit of mass of the International System of Units as precisely 64.79891 milligrams. Thus, there are precisely 7,000 grains per avoirdupois pou... more

A grain is a unit of measurement of mass that is based upon the mass of a single seed of a typical cereal. Historically, in Europe, the average masses of wheat and barley grain were used to define units of mass. Since 1958, the grain or troy grain (Symbol: gr) measure has been redefined on the basis of the unit of mass of the International System of Units as precisely 64.79891 milligrams. Thus, there are precisely 7,000 grains per avoirdupois pound in the Imperial and U.S. customary units. In fact, the grain is the only unit of mass measure common to the traditional three English mass and weight systems (avoirdupois, Apothecaries', troy). Moreover, the measure for pearls and diamonds—the pearl grain and the metric grain—are equal to ⁄4 of a (metric) carat, i.e. 50 mg (0.77 gr). The grain is used to measure the mass of bullets, gunpowder, and smokeless powder; it is the measure used by the balances used in handloading; bullets are measured in increments of one grain, gunpowder in... less