The international avoirdupois ounce (oz) = 28.349523 grams = 437.5 grains (gr). There are 16 ounces in an pound. The ounce is commonly used as a unit of mass in the US, Canada and sometimes in Australia and New Zealand. The troy ounce (symbol and abbreviation: ozt) is a non-SI unit of mass commonly used to gauge the weight of precious metals. One troy ounce (ozt) = 1.09714286 ounces (oz) = 31.1034768 grams (g) = 480 grains (gr).