Dram (dr) - Unit Information & Conversion

Quick Answer

Two different drams exist:

Avoirdupois dram (common commercial use):

• 1 dram = 1/16 ounce = 1/256 pound
• 1 dram ≈ 1.772 grams
• 27.344 grains

Apothecary/Troy dram (historical pharmacy):

• 1 dram (ʒ) = 1/8 apothecary ounce
• 1 dram ≈ 3.888 grams
• 60 grains = 3 scruples

Caution: Always specify which dram! The apothecary dram is more than twice the weight of the avoirdupois dram.

Quick Comparison Table

Unit	Avoirdupois Dram	Apothecary Dram (ʒ)	Grams
1 dram	1 dr av	—	1.772 g
1 apothecary dram	2.194 dr av	1 ʒ	3.888 g
1 grain	0.0366 dr av	0.0167 ʒ	0.0648 g
1 scruple	0.732 dr av	0.333 ʒ	1.296 g
1 ounce (avoirdupois)	16 dr av	7.292 ʒ	28.35 g
1 ounce (apothecary)	17.554 dr av	8 ʒ	31.10 g
1 pound (avoirdupois)	256 dr av	116.67 ʒ	453.59 g
1 pound (troy/apoth.)	210.65 dr av	96 ʒ	373.24 g

Definition

Avoirdupois Dram (Commercial)

The avoirdupois dram is defined in the common weight system used for most goods:

Relationships:

• 1 dram = 1/16 ounce (avoirdupois)
• 1 dram = 1/256 pound (avoirdupois)
• 1 dram = 27.34375 grains (exactly)
• 1 dram ≈ 1.7718451953125 grams (exactly)

Symbol: dr, dr av, or dr avdp

Historical use: General commerce, precious materials, spices, ammunition powder charges.

Apothecary/Troy Dram (Pharmaceutical)

The apothecary dram (also called drachm) belongs to the apothecaries' weight system used historically in pharmacy:

Relationships:

• 1 dram (ʒ) = 1/8 ounce (apothecary)
• 1 dram = 3 scruples
• 1 dram = 60 grains (exactly)
• 1 dram ≈ 3.8879346 grams (exactly)

Symbol: ʒ (resembles the number 3, representing 3 scruples)

Historical use: Compounding medicines, pharmaceutical measurements, medical prescriptions.

The Critical Difference

Apothecary dram = 2.194 × Avoirdupois dram

This 2.2× ratio causes confusion. Historical recipes and medical texts must specify which system they use, or dosages could be dangerously incorrect.

Fluid Dram (Volume, Not Weight)

Adding to the confusion, the fluid dram is a unit of volume:

Fluid dram (imperial):

• 1/8 fluid ounce (imperial)
• ≈ 3.5516 mL

Fluid dram (US):

• 1/8 fluid ounce (US)
• ≈ 3.6967 mL

Symbol: fl dr, fl ʒ, or ℈

This is completely separate from weight drams, though historically related (1 fluid dram of water weighs approximately 1 avoirdupois dram).

History

Ancient Greek Drachma (600 BCE - 300 CE)

The drachma coin: Greek city-states minted silver coins called drachmas, weighing approximately 4.3 grams (varying by region and period).

Origin of name: "Drachma" (δραχμή) derives from "drax" (handful) or "drassomai" (to grasp), possibly referring to a handful of six obol coins.

Weight standard: The Attic drachma (Athens) weighed about 4.3 g of silver, becoming a widespread weight and monetary standard.

Roman Adoption (300 BCE - 500 CE)

Drachma in Roman medicine: Roman physicians adopted Greek medical practices, including pharmaceutical measurements based on the drachma.

Galen's formulations: The physician Galen (129-216 CE) used drachmas extensively in medicinal recipes, establishing the unit in medical tradition.

Byzantine and Islamic Medicine (500-1200 CE)

Byzantine continuation: The Eastern Roman Empire (Byzantium) preserved Greek medical texts, maintaining the drachm as a pharmaceutical unit.

Islamic Golden Age: Arab physicians (Al-Razi, Avicenna) translated Greek medical works, incorporating drachms into Arabic pharmacy. The dirham (Arabic coin) shares the same etymological root.

Transmission to Europe: Through Islamic Spain and Sicily, Arabic medical knowledge returned to Western Europe (11th-13th centuries), bringing pharmaceutical drachm measurements.

Medieval European Apothecaries (1200-1600)

Apothecary guilds: European cities established apothecary guilds, standardizing medicinal weights based on the drachm.

The apothecary system:

• 1 pound (lb ap) = 12 ounces
• 1 ounce (℥) = 8 drams (ʒ)
• 1 dram = 3 scruples (℈)
• 1 scruple = 20 grains (gr)

Result: 1 apothecary dram = 60 grains

Symbol evolution: The symbol ʒ (scribal abbreviation for Latin "drachma") became standard for the dram.

British Standardization (1600-1800)

London Pharmacopoeia (1618): The first official British pharmacopoeia standardized apothecary weights, including the dram at 60 grains.

Avoirdupois emergence: Simultaneously, the avoirdupois system developed for general commerce, creating a different dram:

• Avoirdupois dram = 1/16 ounce = 27.34375 grains

Coexistence: Two dram standards coexisted—apothecary for medicine, avoirdupois for trade.

American Adoption (1776-1900)

U.S. Pharmacopeia (1820): The first U.S. Pharmacopeia codified pharmaceutical measurements, adopting British apothecary standards including the dram.

Medical education: American medical schools taught apothecary measurements. Physicians wrote prescriptions using symbols like ʒ for drams.

Commercial use: Avoirdupois drams measured gunpowder, spices, precious materials, and other commodities.

Ammunition Application (1800s-Present)

Black powder charges: Early firearms used black powder measured in drams. A "3-dram load" meant 3 avoirdupois drams of powder.

Dram equivalent: With the transition to smokeless powder (1880s onward), manufacturers created "dram equivalent" ratings—the amount of smokeless powder producing the same velocity as a given dram measure of black powder.

Modern shotshells: Today's shotgun shells still reference "3 dram equivalent" or "3¼ dram equivalent" on the box, though actual powder weights are in grains or grams.

Metrication and Decline (1900-Present)

British pharmacy (1970): The UK officially abandoned apothecary weights, switching entirely to metric (grams, milligrams).

American pharmacy (1970s-1980s): U.S. pharmacy schools phased out apothecary measurements, adopting metric. By 1990, nearly all prescriptions used metric units.

Persistence:

• Ammunition: Dram equivalent ratings continue
• Historical recipes: Antique cookbooks and medical texts
• Collectors: Antique apothecary scales and weights

Real-World Examples

Avoirdupois Dram Examples

• 1 dram (1.77 g): Small pinch of saffron threads
• 2 drams (3.54 g): Postage stamp weight
• 4 drams (7.09 g): Quarter of an avoirdupois ounce
• 16 drams (28.35 g): One avoirdupois ounce
• 27.34 grains = 1 dram: Used in bullet/powder weight calculations

Apothecary Dram Examples (Historical)

• 1 dram ʒ (3.89 g): Typical dose of powdered herb in 19th-century medicine
• 2 drams ʒ (7.78 g): Common tincture or extract dose
• 60 grains = 1 dram ʒ: Pharmaceutical compounding standard
• 8 drams ʒ (31.1 g): One apothecary ounce

Ammunition Dram Equivalents

Modern shotgun shells:

• 2¾ dram eq: Light target loads (1,200 fps)
• 3 dram eq: Standard field loads (1,250-1,300 fps)
• 3¼ dram eq: Magnum hunting loads (1,300-1,400 fps)
• 3¾ dram eq: Heavy magnum loads (1,400+ fps)

Note: "Dram equivalent" is a velocity rating, not actual powder weight. Modern loads use 15-35 grains of smokeless powder, not drams.

Common Uses

1. Ammunition and Reloading

Shotshell ratings: Manufacturers mark shotgun shells with "dram equivalent" to indicate approximate velocity/power level.

Why still used? Tradition and familiarity. Shooters understand "3 dram load" means standard power, while "3¾ dram" is heavy magnum.

Reloading manuals: Some reloading data references dram equivalents alongside modern grain measurements.

2. Historical Recipe Interpretation

19th-century cookbooks: Recipes may call for "1 dram of nutmeg" or "2 drams of ginger."

Conversion challenge: Must determine if the recipe uses avoirdupois or apothecary drams (usually avoirdupois for cooking).

Modern equivalent: 1 avoirdupois dram ≈ 1.77 grams ≈ 1/3 teaspoon (for dry spices)

3. Antique Apothecary Items

Collectible scales: Antique apothecary scales often have dram weights marked with ʒ.

Medicine bottles: Historical pharmacy bottles may indicate contents in drams.

Historical research: Understanding drams is essential for interpreting 18th-19th century medical texts.

4. Pharmaceutical History

Old pharmacopoeias: Historical pharmaceutical formulas use apothecary drams.

Example prescription (1850s): "℞ Quinine sulfate ʒij" = Take 2 drams of quinine sulfate

Modern interpretation: 2 apothecary drams = 7.78 grams

Conversion Guide

Avoirdupois Dram Conversions

Drams to Grams: Grams = Drams × 1.7718451953125

Examples:

• 1 dr × 1.772 = 1.772 g
• 10 dr × 1.772 = 17.72 g

Drams to Ounces (avoirdupois): Ounces = Drams ÷ 16

Examples:

• 16 dr ÷ 16 = 1 oz
• 8 dr ÷ 16 = 0.5 oz

Drams to Grains: Grains = Drams × 27.34375

Examples:

• 1 dr × 27.344 = 27.344 grains
• 2 dr × 27.344 = 54.688 grains

Apothecary Dram Conversions

Apothecary Drams to Grams: Grams = Drams × 3.8879346

Examples:

• 1 ʒ × 3.888 = 3.888 g
• 2 ʒ × 3.888 = 7.776 g

Apothecary Drams to Grains: Grains = Drams × 60

Examples:

• 1 ʒ × 60 = 60 grains
• 5 ʒ × 60 = 300 grains

Apothecary Drams to Scruples: Scruples = Drams × 3

Examples:

• 1 ʒ × 3 = 3 scruples
• 4 ʒ × 3 = 12 scruples

Between Dram Systems

Apothecary to Avoirdupois: Avoirdupois drams = Apothecary drams × 2.1943

Avoirdupois to Apothecary: Apothecary drams = Avoirdupois drams ÷ 2.1943

Example: 1 apothecary dram = 2.194 avoirdupois drams

Common Conversion Mistakes

1. Confusing Avoirdupois and Apothecary Drams

The Mistake: Assuming all drams are the same

The Danger: Using apothecary dram values where avoirdupois is meant (or vice versa) creates a 2.2× error.

Example error: Historical recipe calls for "1 dram almond extract"

• If apothecary: 3.89 g
• If avoirdupois: 1.77 g
• Difference: 2.2× too much!

The Fix: Check context. Pharmacy = apothecary. General commerce = avoirdupois.

2. Mixing Up Dram (Weight) and Fluid Dram (Volume)

The Mistake: Treating drams as volume when they're weight (or vice versa)

The Problem:

• Dram (dr) = weight (mass)
• Fluid dram (fl dr) = volume

Example error: Recipe says "2 drams water"

• If weight dram: 3.54 grams of water ≈ 3.54 mL
• If fluid dram: 7.39 mL ≈ 7.39 grams
• Difference: 2× error

The Fix: "Dram" alone typically means weight. "Fluid dram" or "fl dr" means volume.

3. Misinterpreting Dram Equivalent in Ammunition

The Mistake: Thinking "3 dram equivalent" means 3 drams of actual powder

The Truth: "Dram equivalent" is a velocity rating, not powder weight.

Reality: A "3 dram equivalent" modern load might contain only 18-20 grains of smokeless powder (about 0.66 avoirdupois drams).

The Fix: Understand dram equivalent as a power/velocity comparison to historical black powder loads, not literal weight.

4. Incorrect Grain-to-Dram Conversion

The Mistake: Using 27.34 grains per dram for apothecary measurements

The Truth:

• Avoirdupois: 27.34375 grains = 1 dram
• Apothecary: 60 grains = 1 dram

Example error: Converting 120 grains apothecary measurement

• Wrong: 120 ÷ 27.34 = 4.39 drams (using wrong system)
• Correct: 120 ÷ 60 = 2 drams apothecary

5. Assuming Modern Medicine Uses Drams

The Mistake: Trying to use drams for current pharmaceutical dosages

The Truth: Modern medicine uses metric exclusively (milligrams, grams, milliliters).

The Fix: Drams are historical only. Contemporary prescriptions never use drams—always convert to metric.