Measurements

English System Measurement Equivalents

Length

1 foot = 12 inches

1 yard = 3 feet = 36 inches

1 mile = 5,280 feet

Weight

1 pound = 16 ounces

1 ton = 2000 pounds

Volume

1 teaspoon = 75 drops

1 tablespoon = 3 teaspoons

1 ounce = 2 tablespoons

1 cup = 8 ounces

1 pint = 2 cups

1 quart = 2 pints

1 gallon = 4 quart

15 drops = 1 mL

Metric System Measurement Equivalents

1 mL = 1 cc = 1 g

length - meters

weight - grams

volume - liters

Apothecary System Measurement Equivalents

Weight

1 dram = 60 grains

1 ounce = 8 drams

1 pound = 12 ounces

Volume

1 fluidram = 60 minims

1 fluidounce = 8 fluidrams

1 pint = 16 fluidounces

1 quart = 2 pints

1 gallon = 4 quarts

Abbreviations

When writing medication dosages, physicians and pharmacists often use abbreviations. A combination of letters, numbers, and symbols are used to make abbreviations in the apothecary system. Roman numerals are used to represent whole numbers. However, unlike standard Roman numerals, which are written with capital letters, the apothecary system uses lower case letters. Another common symbol is ss, which stands for 1/2.

To write abbreviations in the apothecary system, first write the unit of measurement. Then write the amount. Follow these general guidelines for writing amounts in the apothecary system:

• if the amount is 1 or greater, use lower case Roman numerals. for example, 2 drams is written dr ii.
• if the amount is less than 1, use a fraction. for example, 1/4 of an ounce is written oz 1/4.
• if the amount contains the value 1/2, use ss. for example, 1/2 grain is written gr ss, and 2 and 1/2 grains is written gr iiss.