Unlike the ounces you find in grocery stores, a troy ounce is a unit that is commonly used for precious metals like silver bullion and gold bullion. Although their names might not indicate this, these two units are not the same in weight.
While 1 troy ounce (troy oz) of silver is equal to 31.103 grams, 1 ounce (oz) will equal only 28.3495 grams.
The differential of close to 10% makes it absolutely vital for precious metals buyers and sellers to be aware of the differences between these two units.
History of the Avoirdupois Ounce (the grocery store ounce)
This unit is commonly used throughout the USA and is also known as an imperial ounce. The word ‘avoirdupois’ is derived from its Middle-English ancestor – “Avoir de pois.” This means “goods sold by weight.”
An Avoirdupois Ounce is denoted by the symbol “oz.” and equals 28.3495 grams.
The first use of this unit dates back to the early 13th century. It was then updated and made official almost six centuries later. In 1959, the unit was standardized and defined by the countries that agreed to use this unit.
Although many countries have now begun moving away from this system, drawn to the simplicity and widespread use of the metric system, the United States remains loyal to Avoirdupois Pound standard of weights even today.
History of the Troy Ounce
From the beginning, troy ounces have been tied to measuring the weights of precious metals. And every quest to uncover its origin seems to lead researchers towards a trade market in a town called Troyes, in France.
In the 1400s, King Henry II adopted this system of weights as an official standard of measure for gold and silver in Britain. The United States followed suit in 1828. Since then, it has remained one of the most-used weighing system for precious metals. However, some mints like the Chinese Mint, have started switching to the metric system for the sake of standardizing weights.
A troy ounce is denoted by the symbol “troy oz.” or sometimes "ozt" and equals 31.103 grams.
This entire concept may be a bit confusting as all US Bullion Dealers market and advertise gold bullion and silver bullion by the ounce. However, they are actually dealing in troy ounces. For the sake of convenience and simplicity, it has become a US industry standard to refer to troy ounces as simply ounces. But now you know the technical difference :-)