Dram (dr)
The dram (also spelled drachm in British English) is an avoirdupois unit of mass equal to 1/16 of an ounce or approximately 1.772 grams. Once common in pharmacy and trade, the dram has been almost entirely superseded by metric units. It persists in a single niche: the US ammunition industry uses the "dram equivalent" rating for shotgun shells.
Definition
One avoirdupois dram equals exactly 1/16 of an avoirdupois ounce, 27.34375 grains, approximately 1.7718 grams, or 1,771.8 milligrams. There are 16 drams in an ounce and 256 drams in a pound. The apothecaries' dram (60 grains, ~3.888 g) is a different unit and should not be confused with the avoirdupois dram.
History
The dram descends from the ancient Greek drachma, a unit of both weight and currency. In the avoirdupois system, the dram was standardised at 1/16 of an ounce (27.34375 grains). The apothecaries' dram, a different unit of the same name, equalled 1/8 of an apothecaries' ounce (about 3.888 grams). Both versions were widely used in English-speaking pharmacy and trade until metrication rendered them obsolete for most purposes in the 20th century.
Common Uses
The dram's only surviving modern application is the "dram equivalent" rating on US shotgun shells, which indicates the powder charge relative to the original black powder load. Outside of this niche, the dram has no modern applications. Historical pharmacy records and old recipes may reference drams, requiring conversion for modern use.
Did You Know? Facts About Dram
- A "dram" of whisky originally referred to an apothecaries' dram (about 3.9 grams of liquid), but today it simply means a small serving with no precise measurement.
- The shotgun shell "dram equivalent" system dates from the era of black powder and is now purely a performance rating, not an actual weight measurement.
- The word "dram" comes from the Greek drachma, which was both a unit of weight and a silver coin.
- There were actually two different drams: the avoirdupois dram (1.77 g) and the apothecaries' dram (3.89 g) - causing centuries of confusion.
- The dram is one of the smallest imperial weight units that was once in widespread daily use.