Systems of Measure 1

Avoirdupois System – French for goods of weight (goods sold by weight) – Based on the system of weights where 16 ounces equals one (1) pound – Used in the United States, Canada, and Great Britain (although officially adopted Metric System) Metric System – most widely used system of measurement in pharmacy 2

The Metric System Dosage of a drug is usually given in milligrams (mg) Liquid medications are often measured in milliliters (mL) When calculating dosages, you will need to know the client’s weight in kilograms (kg) These units are all metric 3

The Metric System Basic units of measure in metric system are the: – Gram (g) – used for weight or mass – Liter (L) – used to measure volume The metric system is a decimal system – Based on multiples of ten (10) A system of prefixes is used to show how large or small a unit in the metric system is – e.g., one unit of measure is the meter; the prefix hecto- means “100,” and the prefix deci- means 1/10 – Therefore, hectometer means 100 meters, and decimeter means 1/10 th of a meter (or 0.1) 4

The Metric System Converting from one unit to another within metric system, one must know which direction to move decimal point, and how far to move it In text lists prefixes from kilo- to milli-, the meaning of each prefix, and how the prefixes are combined with the base units for weight and volume 5

The Metric System Use following sentence to help you remember the metric prefixes in order from largest to smallest Kate Had Dates who Didn’t Call Much – K – kilo- – H – hecto- – D – deka- – D – deci- – C – centi- – M – milli- Note that the word “who” is used for the space where no prefix is used 6

The Metric System You can also use the sentence to convert units within the metric system 7

Common Measurements 1 tablespoon = 3 teaspoons 1 teaspoon = 5 milliliters 1 tablespoon = 15 milliliters 1 fluid ounce = 2 tablespoons 1 fluid ounce = 30 milliliters 1 pound = 454 grams 1 kilogram = 2.2 pounds 8

Other Measurements MetricHousehold 1 cc or 1 mL15 gtts (drops) 5 cc or 5 mL1 tsp (teaspoon) 15 cc or 15 mL1 tbsp (tablespoon) 30 cc or 30 mL1 oz (ounce) 240 cc or 240 mL1 cup (8 oz) 500 cc or 500 mL1 pt (pint) (16 oz) 1,000 cc or 1,000 mL1 qt (quart)(32 oz) 9

Other Systems of Measure Household System – Includes measurements used in kitchen – Examples are teaspoon and tablespoon Avoirdupois System – Measures units such as fluid ounce and pound Apothecary System – Seldom used – Ancient system based on minim (volume) and grain (weight) 10

Measurement You are making a measurement when you Check you weight Read your watch Take your temperature What kinds of measurements did you make today? 11

Standards of Measurement When we measure, we use a measuring tool to compare some dimension of an object to a standard. 12

Some Tools for Measurement 13

Stating a Measurement In every measurement there is a Number followed by a Unit from measuring device 14