金衡制是一种通常使用在金、银、黑火药及宝石的质量单位系统。

金衡制系统来自质量计量的金衡制系统。名字来源还要回溯到威廉一世时代法国的特鲁瓦，在中世纪时期，特鲁瓦是重要贸易城市。

Troy weight is a system of units of mass customarily used for precious metals and gemstones. There are 12 troy ounces per troy pound, (373.24 g) rather than the 16 ounces per pound (453.59 g) found in the more common avoirdupois system. The troy ounce is 480 grains, compared with the avoirdupois ounce, which is 437 ⁄₂ grains. Both systems use the same grain defined by the international yard and pound agreement of 1959 as exactly 0.064 798 91 gram. Although troy ounces are still used to weigh gold, silver, and gemstones, troy weight is no longer used in most other applications.