Troy weight Troy weight Troy weight is a system of units of mass customarily used for precious metals and gemstones. One troy ounce (abbreviated "t oz" or "oz t") is equal to exactly , (or about 1.0971 oz. avoirdupois, the "avoirdupois" ounce being the most common definition of an "ounce" in the US). There are only 12 troy ounces per troy pound, rather than the 16 ounces per pound found in the more common avoirdupois system. The avoirdupois pound has 7000 grains whereas the troy pound has only 5760 grains (i.e. 12 × 480 grains). Both systems use the same grain defined
Pound (mass) and for different applications, the pound (or its translation) has referred to broadly similar but not identical standards of mass or force. The libra (Latin for "scales / balance") is an ancient Roman unit of mass that was equivalent to approximately 328.9 grams. It was divided into 12 "unciae" (singular: "uncia"), or ounces. The "libra" is the origin of the abbreviation for pound, "lb". A number of different definitions of the pound have historically been used in Britain. Amongst these were the avoirdupois pound and the obsolete Tower, merchant's and London pounds. Troy pounds and ounces remain in use only