A troy ounce is a unit of weight commonly used to measure precious metals like gold, silver, and platinum. It is part of the troy weight system, which dates back to the Middle Ages and was originally used in the trading of goods. One troy ounce is equivalent to approximately 31.1035 grams. Unlike the more common avoirdupois ounce, which is used for everyday items, the troy ounce is specifically designed for precious metals. There are 12 troy ounces in a troy pound, making it distinct from the avoirdupois system, which has 16 ounces in a pound.