Troy weight

Troy weight is a system of units of mass customarily used for precious metals, black powder, and gemstones. Named after Troyes, France, the troy system of weights was known to exist in medieval times, at the celebrated fair at Troyes in North Eastern France. One cubic inch of distilled water, at 62 °F (17 °C), and at a barometric pressure of 30 inches of mercury, was determined to weigh 252.458 troy grains (gr). There are 24 grains in 1 dwt, and ... more

Troy weight is a system of units of mass customarily used for precious metals, black powder, and gemstones. Named after Troyes, France, the troy system of weights was known to exist in medieval times, at the celebrated fair at Troyes in North Eastern France. One cubic inch of distilled water, at 62 °F (17 °C), and at a barometric pressure of 30 inches of mercury, was determined to weigh 252.458 troy grains (gr). There are 24 grains in 1 dwt, and 20 dwt in one troy ounce. Because there were 12 troy ounces in the old troy pound, there would have been 240 pennyweights to the pound — the basis of the fact that the old British pound (currency) contained 240 pence. The 'd' in dwt is for denarius, the ancient Roman coin equivalent to a penny. The troy pound (troy) is 5,760 gr (≈ 373.24 g, 12 ozt), while an avoirdupois pound is heavier at 7,000 gr (≈ 453.59 g). There are 12 troy ounces per troy pound, rather than 16 avoirdupois ounces (oz) in the avoirdupois pound (lb) as in the more common... less