See also pearl grain and colonial grain.


Convert between grains and other major units of mass.

In the English-speaking world, before 13th century – present, the smallest unit of mass in the customary systems of weights, since 1959 = 64.79891 milligrams exactly. Abbr, gr. Its subdivisions—see moneyer's weight—are largely imaginary. The grain is the common element in troy, apothecaries', and avoirdupois weight: the troy and apothecaries' pound are 5,760 grains, and the pound avoirdupois is 7,000 grains.

Traditionally, the grain was thought of as the weight of a barleycorn taken from the middle of the ear.

In the United Kingdom, the Weights and Measures Act, 1985, prohibited further use of the grain in trade. In the United States it remains the customary unit for expressing, for example, the weight of bullets.


In France, a very small unit of mass, varying over time link to a chart showing relationships between the livre and its subdivisions at various periods:

The French grain is, conceptually, the mass of a grain of wheat, just as the English grain was conceptually the mass of a barleycorn.

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