Since the implementation of the international yard and pound agreement of 1959, a grain has been defined as exactly 64. 79891 milligrams ( mg ); hence one troy ounce is 31. 1034768 grams ( g ) ( exact by definition ), about 10 percent more than the avoirdupois ounce, which is 28. 349523125 g ( exact ).

Since the implementation of the international yard and pound agreement of 1 July 1959, the grain or troy grain ( Symbol: gr ) measure has been defined in terms of units of mass in the International System of Units as precisely.

0.037 seconds.