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.1 One standard ounce, used to weigh other items such as sugar and grain, is slightly less at 28.35 grams.2 The troy ounce is retained even today as the standard unit of measurement in the precious metals market to ensure purity standards and other common measures remain consistent over time. The troy ounce is often abbreviated to read "t oz" or "oz t."
Understanding Troy Ounce
Some historians 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 this new monetary system using the same weights as their Roman ancestors.
Just The Facts
The troy ounce is a metric used in weighing precious metals.
The troy ounce is the equivalent of 31.1034768 grams, whereas the ounce is the equivalent of 28.349 grams.12
A troy pound (12 troy ounces) is lighter than a standard pound (14.6 troy ounces).34
The troy ounce is the last remaining metric still used in the troy weighting system.
The 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.