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A pennyweight (dwt) is a unit of mass equal to 24 grains, 1 ⁄ 20 of a troy ounce, 1 ⁄ 240 of a troy pound, approximately 0.054857 avoirdupois ounce [1] and exactly 1.55517384 grams. [2] It is abbreviated dwt, d standing for denarius – (an ancient Roman coin), and later used as the symbol of an old British penny (see £sd).
The troy weight units are the grain, the pennyweight (24 grains), the troy ounce (20 pennyweights), and the troy pound (12 troy ounces). The troy grain is equal to the grain unit of the avoirdupois system, but the troy ounce is heavier than the avoirdupois ounce, and the troy pound is lighter than the avoirdupois pound. Legally, one troy ounce ...
troy ounce: ozt ozt 1.0 ozt (1.1 oz; 31 g) pennyweight: dwt dwt 1.0 ...
Another difference arose when Britain abolished the troy pound (373.241 7216 g) on 1 January 1879, leaving only the troy ounce (31.103 4768 g) and its decimal subdivisions, whereas the troy pound (of 12 troy ounces) and pennyweight are still legal in the United States, although they are no longer widely used.
The teaspoon, tablespoon, and cup are defined in terms of a fluid ounce as 1 ⁄ 6, 1 ⁄ 2, and 8 fluid ounces respectively. The fluid ounce derives its name originally from being the volume of one ounce avoirdupois of water, [21] but in the US it is defined as 1 ⁄ 128 of a US gallon. Consequently, a fluid ounce of water weighs about 1.041 ...
This value was subsequently called the pennyweight and formed the basis of the Troy units of weight—the troy ounce used to this day for weighting precious metals. [ 3 ] : 44–48 Edward I (1272–1307) broke the link between a coin's value and its weight when he debased the English coinage by introducing a groat (four pence) which weighed of ...
"grains troy" distinguishes from other grains, like "grains tower", "grains avoirdupoise" (which was proposed but never used), and "baker's grains". The avoirdupoise dram was to be divided into 30 grains avoir, or into 28 grains in Baker's Tables (in notes on rifle guns). Tower grains are 1/640 tower ounce, or 1/682.666 troy ounce.
English-speaking countries also used a system of units of fluid measure, or in modern terminology volume units, based on the apothecaries' system. Originally, the terms and symbols used to describe the volume measurements of liquids were the same as or similar to those used to describe weight measurements of solids [33] (for example, the pound by weight and the fluid pint were both referred to ...