what is a troy ounce 
a troy ounce is a unit of measure used for weighing precious metals that dates back to the middle ages originally used in troyes france one troy ounce is equal to 31 1034768 grams according to the u k royal mint 1one standard ounce also known as an avordupois ounce is used to weigh other commodities such as sugar and grain a standard ounce is slightly less than a troy ounce at 28 35 grams the troy ounce is to this day the standard unit of measurement in the precious metals market to ensure purity standards the troy ounce is often abbreviated to read t oz or oz t understanding the troy ouncethe troy ounce is the only measure of the troy weighting system that is still used in modern times it is used in the pricing of metals such as gold platinum and silver thus when prices of precious metals are listed per ounce it is often referencing the troy ounce it was also used when weighing certain gemstones the troy weight system however has largely been replaced by the carat system in the world of precious gems and stones history of the troy ouncethe troy system for weights and measures is believed to have gotten its name from the french city of troyes a business hub in the middle ages that attracted merchants from around europe and britain 2 in troyes merchants measured 480 grains of barley to equal a troy ounce and 12 troy ounces equaled one troy pound some historians however believe the troy ounce had its origins in roman times romans standardized their monetary system using bronze bars that could be broken down into 12 pieces called uncia or ounce with each piece weighing around 31 1 grams as europe s economic importance grew from the 10th century onward merchants came from all over the world to buy and sell goods there it was therefore necessary to develop a new standardized monetary weight system to make doing business much easier some believe the merchants of troyes modeled their new monetary system on the weights developed by their roman ancestors before the adoption of the metric system across europe the french born king henry ii of england adjusted the british coinage system to better reflect the french troy system the system was adjusted periodically but troy weights as we know them today were first used in england in the 15th century prior to the adoption of the troy system the british used an anglo norman french system called the avoirdupois system the word means goods of weight and was used to weigh both precious metals and non precious metal goods by 1527 the troy ounce became the official standard measurement for gold and silver in britain and the u s followed suit in 1828 3troy ounce vs ouncethe avoirdupois ounce simply referred to as ounce oz is the standard used in the us to measure foods and other items with the exception of precious metals and gems it is the equivalent of 28 349 grams or 437 5 grains a troy ounce is a little heavier with a gram equivalent of 31 1 the difference 2 751 may be minute for a small quantity but can be substantial for large quantities 4