# Apothecaries and Troy Conversion Calculator

To use the calculator, place your cursor in the desired unit field and write a number. If needed use the dot "." as the decimal separator.

lb t
oz t
dr
dwt
s ap
gr

## Did you know?

Use the overview below to better understand the meaning and history of the different weight units.

• ##### Troy Pound `(373.2417 grams)`
The troy pound is 5 760 grains (≈ 373.24 g, 12 oz t), while an avoirdupois pound is approximately 21.53% heavier at 7 000 grains (≈ 453.59 g).
• ##### Troy Ounce `(31.10 grams)`
Troy weight is a system of units of mass customarily used for precious metals and gemstones. One troy ounce (abbreviated "t oz" or "oz t") is equal to 31.1034768 grams, (or about 1.0971 oz. avoirdupois, the "avoirdupois" ounce being the most common definition of an "ounce" in the US). There are only 12 troy ounces per troy pound, rather than the 16 ounces per pound found in the more common avoirdupois system. However, the avoirdupois pound has 7000 grains whereas the troy pound has only 5760 grains (i.e. 12 × 480 grains). Both systems use the same grain defined by the international yard and pound agreement of 1959 as 0.06479891 grams. Therefore, the troy ounce is 480 grains or 31.10 grams, compared with the avoirdupois ounce, which is 437.5 grains or 28.35 grams. The troy ounce, then, is about 10% heavier (ratio 192/175) than the avoirdupois ounce. Although troy ounces are still used to weigh gold, silver, and gemstones, troy weight is no longer used in most other applications. One troy ounce of gold is denoted with the ISO 4217 currency code XAU, while one troy ounce of silver is denoted as XAG.
• ##### Dram `(3.888 grams)`
The apothecaries' system or apothecaries' weights and measures is a historical system of mass and volume units that were used by physicians and apothecaries for medical recipes, and also sometimes by scientists. Dram, unit of weight in the apothecaries’ and avoirdupois systems. An apothecaries’ dram contains 3 scruples (3.888 grams) of 20 grains each and is equal to one-eighth apothecaries’ ounce of 480 grains.
• ##### Pennyweight `(1.5552 gram)`
The pennyweight symbol is dwt. 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 sterling of currency contained 240 pence. (However, prior to 1526, English pound sterling was based on the tower pound, which is 15⁄16 of a troy pound.) The d in dwt stands for denarius, the ancient Roman coin, referred to in the New Testament, that equates loosely to a penny. The symbol d for penny can be recognized in the notation for British pre-decimal pennies, in which pounds, shillings, and pence were indicated using the symbols £, s, and d, respectively. For example, £6 11s 8d indicated six pounds, eleven shillings, and eight pence.
• ##### Scruple `(1.296 grams)`
The apothecaries' system or apothecaries' weights and measures is a historical system of mass and volume units that were used by physicians and apothecaries for medical recipes, and also sometimes by scientists. Scruple, unit of weight in the apothecaries’ system, equal to 20 grains, or one-third dram, and equivalent to 1.296 grams.
• ##### Grain `(0.0648 grams)`
The small golden disk close to the 5 cm marker is a piece of pure gold weighing one troy grain. Shown for comparison is a tape measure and coins of major world currencies. A grain is a unit of measurement of mass, and in the troy weight, avoirdupois, and Apothecaries' system, equal to exactly 64.79891 milligrams. It is nominally based upon the mass of a single virtual ideal seed of a cereal. From the Bronze Age into the Renaissance the average masses of wheat and barley grains were part of the legal definitions of units of mass. Rather, expressions such as "thirty-two grains of wheat, taken from the middle of the ear" appear to have been ritualistic formulas, essentially the premodern equivalent of legal boilerplate. Another source states that it was defined as the weight needed for 252.458 units to balance a cubic inch of distilled water at 30 inches of mercury pressure and 62 degrees Fahrenheit for both the air and water. Another book states that Captain Henry Kater, of the British Standards Commission, arrived at this value experimentally.
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