Gold is measured using troy ounces, not the everyday ounces used for groceries. A troy ounce equals 31.1 grams, while a standard ounce equals 28.35 grams. This doesn’t mean gold is heavier or denser—it simply uses a different historical weight standard that ensures consistency in precious-metal trading worldwide.
This dates back to 9th century French measuring systems. The 'troy' ounce originated from Troyes, France thus the similarity in name. It helped bring a sense of standardization and uniformity to an economy that used to only treat gold and silver as their form of money.
