Pennyweight Pennyweight A pennyweight (abbreviated dwt, from denarius weight) is a unit of mass that is equal to 24 grains, of a troy ounce, of a troy pound, approximately 0.054857 avoirdupois ounce and exactly 1.55517384 grams. In the Middle Ages, a British penny's weight was literally, as well as monetarily, of an ounce and of a pound of sterling silver. At that time, the pound in use was the Tower pound, equal to 7,680 Tower grains (also known as wheat grains). The medieval English pennyweight was thus equal to 32 Tower grains. When Troy weights replaced Tower weights in 1527, the
Grain (unit) weight) refers to those things measured by the lesser but quicker balances: the bismar or uncel, the Roman balance, and the steelyard. The original mercantile pound of 25 shillings or 15 (tower) ounces was displaced by variously the pound of the Hanseatic League (16 tower ounces) and by the pound of the then-important wool trade (16 ounces of 437 grains). A new pound of grains was inadvertently created as 16 troy ounces, referring to the new troy rather than the old troy. Eventually, the wool pound won out. The avoirdupois pound was defined in prototype, rated as to grains. In