What is the difference between troy ounce and a ounce?

The troy ounce (oz t) is a unit of imperial measure. It is normally used to gauge the mass of precious metals. One troy ounce is defined as exactly 0.0311034768 kg or 31.1034768 grams. There are about 32.15 troy oz in 1 kg. One troy ounce is equivalent to approximately 1.09714 avoirdupois ('regular') ounces.