A Simple Guide to Calculations for Pharmacy Technicians

Types of Calculations

• Pharmacy technicians must demonstrate the ability to set up simple equations and solve problems related to determining daily supply of a medicine, deciding pediatric dosages, drip rates and alligation, (the method of solving arithmetic problems related to mixtures of ingredients). The chief calculations made by pharmacy technicians concern measures and conversions.

Metric System

• Volume

  1 liter = 1000 milliliters

  1 milliliter = 1 cubic centimeter

  Weight

  1 gram = 1000 milligrams

  1 milligram = 1000 micrograms

  Household:

  Volume

  1 gallon = 4 quarts

  1 quart = 2 pints

  1 pint = 2 cups = 16 fluid ounces

  1 fluid ounce = 2 tablespoons = 6 teaspoons

  Weight

  1 pound = 16 ounces

  Length

  1 yard = 3 feet

  1 foot = 12 inches

  Conversions

  Household-> Apothecary-> Metric

  Volume

  1 quart = 32 fluid ounces = 0.96 liter

  1 pint = 16 fluid ounces = 480 milliliters *

  1 cup = 8 fluid ounces = 240 milliliters

  2 tablespoons = 1 fluid ounce

  6 fluid grams = 1 fluid ounce = 30 milliliters *

  1 tablespoon = 3 fluid grams = 15 milliliters

  1 teaspoon =1 fluidram = 5 milliliters **

  1 minim = 0.0625 milliliters

  Weight

  2.2 pounds = 1 kilogram

  1 pound = 454 grams

  1 ounce = 8 drams = 30 grams

  Length

  1 inch = 2.5 centimeters

  * In reality, less than 30 milliliters exist in 1 fluid ounce, but 30 milliliters is the standard amount. Drug companies present 473 milliliters, rather than 480 milliliters.

  ** Actually, 3.75 mL make up an apothecary fluidram. Conventional wisdom dictates 1 fluidram = 5 mL = 1 teaspoon.

Avoirdupois System

• Calculate for weight only; primarily used for compounding.

  437.5 gr = 1oz = 28.35 gm

  7000gr = 1lb = 16oz = 454 gm

  1kg = 2.2lb

  1gr = 64.8mg

Apothecary System

• Calculated for volume and weight; utilized for compounding and concentration of diluted mixtures.

  VOLUME

  1 teaspoon (tsp) = 5 milliliters (ml) = 1 dram = 5 cubic centimeters (cc)

  1 tablespoon (tbsp) = 15 milliliters (ml)

  29.57milliliters (ml) = 1 fluid ounce (fl oz)

  473 milliliters (ml) = 1 pint (pt) = 16 fluid ounce (fl oz)

  946 milliliters = 1 quart = 2 pints

  3784 milliliters = 1 gallon = 8 pints = 128 fl oz

  WEIGHT

  1 gr = 64.8 mg

  1 ounce = 31.1 gm = 480 gr