Chapter 3

Measurement Systems and Conversion Procedures

Objectives

Interpret the systems of measurement Simplify units using dimensional analysis Perform metric system conversions Perform conversions between metric and

nonmetric systems

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Objectives (cont’d.)

Perform conversions between apothecary and household systems

Perform temperature conversions between Celsius, Fahrenheit and Kelvin

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Systems of Measurement United States Customary System of

Measurement:• Distance:

– 1 ft = 12 in– 1 yd = 3 ft– 1 mi = 5280 ft

• Volume:– 8 fl oz = 1 cup– 1 pt = 2 cups– 1 qt = 2 pt– 4 qt = 1 gal

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Systems of Measurement (cont’d.) Metric system:

• m → meter → Length• l or L → liter → Volume• g → gram → Weight

– 0.91 m = 1 yd– 3.79 L = 1 gal– 28.3 g = 1 oz

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Systems of Measurement (cont’d.)

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Table 3.1 Metric Prefixes and Values

Basic Dimensional Analysis Algebraically changing or converting units

of measure• .• .

• Grams per liter

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Conversions Within the Metric Systems Horizontal format:

1. Identify decimal location in the number being converted

2. Identify prefix location on horizontal diagram3. Find the difference between the two exponents

associated with each prefix

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Conversions Within the Metric Systems (cont’d.)

Horizontal format:4. Conversion is moving right on the diagram:

– Move decimal to the right by the amount calculated in step 3

5. Conversion is moving left on the diagram:– Move the decimal to the left by the amount

calculated in step 3

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Figure 3.1 Horizontal format for metric prefixes and values

Conversions Within the Metric Systems (cont’d.)

Horizontal format: (cont’d.)• Convert 12 mL to microliters

– Identify decimal: 12.0– Identify prefixes in diagram– Difference is -3 –(-6) = 3– 12 mL = 12,000 μL

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Conversions Within the Metric Systems (cont’d.)

Dimensional analysis:• 1 will always be placed with two-letter unit

Convert: 12μL to mL• .

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Conversions Between Metric and Nonmetric

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Table 3.2 Relationships between the U.S. System and the Metric System

Conversions Between Metric and Nonmetric (cont’d.)

Convert 5 kg to oz:• Convert kg to lbs

• Convert lbs to oz

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Apothecary Systems Apothecary equivalents:

• 1 fl oz = 8 fl dr• 4 mL = 1 fl dr• 60 minims = 1 fl dr• 1 g = 15 gr• 1 gr = 60 mg• 1 mL = 16 minims• 1 pt = 16 fl oz• 1 qt = 2 pt

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Apothecary Systems (cont’d.) 50mg is how many grains?

• .

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Apothecary Systems (cont’d.) 250 fl dr equals how many milliliters?

• .

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Household Systems Household equivalents:

• 60 drops (gtt) = 1 tsp• 1 fl oz = 30 mL• 2 tbs = 1 oz• 6 fl oz = 1 teacup• 8 fl oz = 1 glass• 16 oz = 1 lb• 1 cup = 8 fl oz• 5 mL = 1 tsp

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Household Systems (cont’d.) You drank 3 ½ glasses of water

• How many ounces did you consume?• .

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Household Systems (cont’d.) How many tablespoons are in 12oz?

• .

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Household, Apothecary, and Metric Equivalents

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Temperature Conversions

Three scales to measure temperature:• Fahrenheit• Celsius• Kelvin

Converting Celsius to Fahrenheit:• . or

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Temperature Conversions (cont’d.)

0°C equals how many °F?• °F = (0° × 1.8) + 32°= 0° + 32° = 32°

75°F equals how many °C?• .

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Temperature Conversions (cont’d.)

Converting Celsius to Kelvin:• K = °C + 273.15• 100°C

K = 100° + 273.15° = 373.15°

• Converting Kelvin to Fahrenheit:• °F = 1.8K − 459.67°• 300K

°F = 1.8(300°) − 459.67° = 80.33°

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Summary To perform metric conversions, we must

be familiar with Table 3.1 Conversions within the metric system can

be done using the horizontal format Apothecary system: used in calculating

drug dosages Household system: used when

administering medications in the home

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Summary (cont’d.) The three main temperature formulas:

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