- Dram (unit)
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For the related unit of currency, see Drachma.
The dram (archaic spelling drachm; apothecary symbol ℨ) was historically both a coin and a weight. Currently it is both a small mass in the Apothecaries' system of weights and a small unit of volume. This unit is called more correctly fluid dram or in contraction also fluidram.
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Ancient unit of mass
- The Greek drachm is a weight of 1⁄100 Greek mine, which is about 4.37 grams.
- The Roman drachm is a weight of 1⁄96 Roman pounds, which is about 3.41 grams.
Greek and Roman drachm are related by the approximate ratio 32 : 25.
The Ottoman dirhem is based on the Sassanian drachm, which is itself based on the Roman dram/drachm. Modern Armenian drams, the currency of the Republic of Armenia, share this origin.
Modern unit of mass
In the avoirdupois system, the dram is the mass of 1⁄256 pound or 1⁄16 ounce. So the dram weighs 875⁄32 grains or exactly 1.771 845 195 312 5 grams.
The dram is also the mass of 1⁄96 pound (℔) or 1⁄8 ounce (℥) in the apothecaries' system that survived until the middle of the 20th century in English-speaking countries. It is equal to 3 scruples (℈) or 60 grains (G). Thus, it is equal to exactly 3.887 9346 grams.
Unit of volume
The fluid dram is defined as 1⁄8 of a fluid ounce, which means it is exactly equal to
- 3.696 691 195 312 5 mL in the United States and
- 3.551 632 812 500 0 mL in the Commonwealth and Ireland.
In the United Kingdom, a teaspoon was formerly defined as one and one half fluid dram (it is now 5 mL).
"Dram" is also used as a measure of the powder charge in a shotgun shell.
4 Drams is the measurement of 1/2 a bottle of promoter.
Dram is also used informally to mean a small amount of liquid, especially Scotch whisky. In this case the "dram" will usually be 30 ml - see Alcoholic spirits measures.
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See also
- Avoirdupois
- Imperial unit
- U.S. customary units
Categories:- Units of mass
- Units of volume
- Imperial units
- Customary units in the United States
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