TheFreeWindows Weight Converter is a free service, that will help you convert between Metric, Troy and Avoirdupois weight. Fill whatever measure you know and press the "Convert" button to see the equivalent in all the other measures. The metric system is based on grams, and the avoirdupois system is based on pounds. One troy ounce is equivalent to approximately 1.09714 avoirdupois ounces. Troy weight is a system of units of mass customarily used for precious metals and gemstones. There are 12 troy ounces per troy pound, (373.24 g) rather than the 16 ounces per pound (453.59 g) found in the more common avoirdupois system.