chapter 8

Elsevier items and derived items © 2009 by Saunders, an imprint of Elsevier Inc. Some material was previously published.

Slide 1

Chapter 8Chapter 8

Converting Between Measurement Converting Between Measurement SystemsSystems

Conversion within and among Conversion within and among measurement systems is often necessary measurement systems is often necessary

when preparing medications for when preparing medications for administration. Discuss the steps that the administration. Discuss the steps that the allied health professional should follow to allied health professional should follow to

ensure that such conversions are as ensure that such conversions are as accurate as possible. What are the accurate as possible. What are the

possible sources of error in conversions, possible sources of error in conversions, and how can they be avoided through and how can they be avoided through

professional practice?professional practice?


Slide 2

Learning ObjectivesLearning Objectives

Reading the time of day on the international standard Reading the time of day on the international standard 24-hour clock and converting to the 12-hour clock and 24-hour clock and converting to the 12-hour clock and converting between the two time standardsconverting between the two time standards

Reading a thermometer in Fahrenheit scale and in Reading a thermometer in Fahrenheit scale and in Celsius scale and converting measurements between Celsius scale and converting measurements between the two systems.the two systems.

Converting from one length unit to another within and Converting from one length unit to another within and between the metric and the household systems.between the metric and the household systems.

Converting from one weight or volume unit to another Converting from one weight or volume unit to another within and between the metric system and the within and between the metric system and the household system or the metric system and the household system or the metric system and the apothecary system.apothecary system.


Slide 3

Learning Objectives (cont’d.)Learning Objectives (cont’d.)

Computing approximate equivalents between Computing approximate equivalents between the metric and household systems.the metric and household systems.

Converting approximate equivalents between Converting approximate equivalents between the metric and apothecary systems.the metric and apothecary systems.

Converting approximate equivalents between Converting approximate equivalents between the household and apothecary systems.the household and apothecary systems.


Slide 4

Chapter 8Chapter 8

Lesson 8.1Lesson 8.1


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ConversionConversion

To change from one form to another.To change from one form to another. Necessary in medical field; no world Necessary in medical field; no world

standard.standard. When numbers are converted from one When numbers are converted from one

system to another, they will be approximately system to another, they will be approximately equal.equal.

Conversions that are approximately equal Conversions that are approximately equal may differ by as much as 10%.may differ by as much as 10%.


Slide 6

Figure 8-1.

Time Conversions: 24-Hour ClockTime Conversions: 24-Hour Clock


Slide 7

Standard Clock versus International Standard Clock versus International ClockClock


Slide 8

4:40 AM = 04404:40 AM = 0440

6:25 PM = 18256:25 PM = 1825

11:02 AM = 110211:02 AM = 1102

2:56 AM = 02562:56 AM = 0256

10:45 PM = 224510:45 PM = 2245

8:10 PM = 20108:10 PM = 2010

12:33 AM = 003312:33 AM = 0033

10:00 AM = 100010:00 AM = 1000

3:33 PM = 15333:33 PM = 1533

7:17 AM = 07177:17 AM = 0717

Check Your UnderstandingCheck Your Understanding


Slide 9

Celsius TemperatureCelsius Temperature

In the metric system, temperature is In the metric system, temperature is measured using the Celsius scale measured using the Celsius scale

0° Celsius = 32° Fahrenheit0° Celsius = 32° Fahrenheit


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EXAMPLE: 104°F = _____°CEXAMPLE: 104°F = _____°C

FORMULA: CFORMULA: C° = 5/9 (F° – 32) ° = 5/9 (F° – 32)

SOLUTION: SOLUTION:

5/9(104° – 32) = °C5/9(104° – 32) = °C

5/9 x 72 = °C5/9 x 72 = °C

(72 x 5) ÷ 9 = °C (72 x 5) ÷ 9 = °C

360 ÷ 9 = 40360 ÷ 9 = 40

104°F = 40°C104°F = 40°C

(Alternative: subtract 32 from F° and (Alternative: subtract 32 from F° and divide by 1.8)divide by 1.8)

Fahrenheit to CelsiusFahrenheit to Celsius


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FORMULA: FFORMULA: F° =(9/5 C°) + 32 ° =(9/5 C°) + 32

38.3°C = ______°F 38.3°C = ______°F

(9/5 x 38.3) + 32(9/5 x 38.3) + 3238.3 x 9 = 344.738.3 x 9 = 344.7344.7 ÷ 5 = 68.94344.7 ÷ 5 = 68.9468.94 + 32 = 100.9468.94 + 32 = 100.94Round to 101.0°FRound to 101.0°F38.3°C = 101°F 38.3°C = 101°F

(May also multiply C° by 1.8 and add 32)(May also multiply C° by 1.8 and add 32)

Celsius to FahrenheitCelsius to Fahrenheit


Slide 12

Review of Changing TemperatureReview of Changing Temperature

From C° to F°From C° to F° Multiply C ° by 1.8Multiply C ° by 1.8 Add 32Add 32

From F° to C°From F° to C° Subtract 32 from F °Subtract 32 from F ° Divide by 1.8Divide by 1.8

When performing temperature conversions, When performing temperature conversions, remember to complete the steps in the order given remember to complete the steps in the order given by first removing the parenthesis.by first removing the parenthesis.


Slide 13

Ratios and ProportionsRatios and Proportions

Used to convert when the dosage available is Used to convert when the dosage available is not in the same measurement unit as the not in the same measurement unit as the doctor prescribed.doctor prescribed.

Ratio: expression comparing two quantitiesRatio: expression comparing two quantities Proportion: comparing two equivalent Proportion: comparing two equivalent

fractions or ratiosfractions or ratios


Slide 14

Solving Unknown VariablesSolving Unknown Variables

Numerators must be of the Numerators must be of the same units.same units.

Denominators should be of Denominators should be of the same units.the same units.

1 mL : 15 gtts is the same 1 mL : 15 gtts is the same as 2 mL : 30 gttsas 2 mL : 30 gtts

1 mL/15 gtts = 2 mL/30 gtts1 mL/15 gtts = 2 mL/30 gtts


Slide 15

Solving Unknown Variables (cont’d.)Solving Unknown Variables (cont’d.)


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Using Ratio/ProportionUsing Ratio/Proportion

When setting up both ratios, be sure to label When setting up both ratios, be sure to label all of the terms, including x with the correct all of the terms, including x with the correct measurement to ensure that the equations measurement to ensure that the equations are equivalents.are equivalents.


Slide 17

Common Measurements Used in Common Measurements Used in ConversionsConversions


Slide 18

Volume ConversionsVolume Conversions


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ffʒʒ x = ______ mL x = ______ mL Remember, this is 10 fluid dramsRemember, this is 10 fluid drams 4 mL = f4 mL = fʒʒ ii 4 mL / f4 mL / fʒʒ i = i = xx mL / f mL / fʒʒ xx

4 x 10 = 404 x 10 = 40 1 x 1 x xx = = xx 1 1 xx = 4 x 10 = 40 = 4 x 10 = 40 ffʒʒ xx = 40 mL = 40 mL

4 mL x mLfʒ x 1 fʒ 10

Volume Conversions – Apothecary to Volume Conversions – Apothecary to MetricMetric


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Volume Conversions – Metric to Volume Conversions – Metric to HouseholdHousehold

Known amounts – 1 pint = 500 mlKnown amounts – 1 pint = 500 ml Insert equation in Example 9 p. 153Insert equation in Example 9 p. 153 Add cross multiplicationAdd cross multiplication 500 500 xx = 750 = 750 xx = 750/500 = 750/500 xx = 1.5 pt = 1.5 pt


Slide 21

Conversion Clock for Liquid Volumes Conversion Clock for Liquid Volumes

for Metric and Apothecary Systemsfor Metric and Apothecary Systems


Slide 22

Weight Measurements between Weight Measurements between Metric and Household SystemsMetric and Household Systems

The conversion for metric system to The conversion for metric system to household system ishousehold system is 2.2# = I kg2.2# = I kg 206# = ____ kg206# = ____ kg 2.2#/ 1 kg = 206# / x kg2.2#/ 1 kg = 206# / x kg 2.2 x = 2062.2 x = 206 x = 206/2.2x = 206/2.2 x = 93.6 kgx = 93.6 kg


Slide 23

Conversion Factors for Length Conversion Factors for Length Measurements – Metric to Measurements – Metric to

HouseholdHousehold


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An abdominal cavity was opened with a 14-inch incision. Convert this An abdominal cavity was opened with a 14-inch incision. Convert this measurement into cm.measurement into cm.

• 2.5 cm = 1 inch• 2.5 cm / 1 in = x cm / 14 in•

• 2.5 x 14 = 35• 1 x x = x• x = 35• 14 inches = 35 cm

2.5 cm x cm1 in 14 in

Length ConversionsLength Conversions

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