Gold and silver are measured by weight (or mass, to be pedantic). The units are grains and troy ounces. There are 480 grains to one troy ounce, and twelve troy ounces to one troy pound. In standard terms, this means one troy ounce is 31.10 grams, which is about 10% heavier than one ‘normal’ (or avoirdupois) ounce of 28.35 grams.
