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Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 1
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 2
Chapter 4 Comparisons of
Measurement Systems
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 3
Learning Objectives
• Know the standard abbreviations for the household, metric, and apothecary systems used in the medical field
• Identify and use the household measurements of length, weight, and volume in the medical field
• Identify and use the International System of Units (SI), or metric, measurements of length, weight, and volume in the medical field
• Identify and use apothecary system measurements of weight and volume in the medical field
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 4
Common Measurement Systems
• Household or U.S. customary• Metric• Apothecary
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 5
Household Measurement System
• Based on English system of measures
• Expressed as Arabic numbers preceding abbreviations (e.g., 5 inches)
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Household Measurements of Weight
Measurement Unit Abbreviation Equivalentsounce oz —
pound lb, # 16 oz
ton T 2000#
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Household Measurements of Length
Measurement Unit Abbreviation Equivalentsinches in, ” —
foot ft, ’ 12 inches
yard yd 36 inches, 3 feet
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 8
Household Measurements of Volume
Measurement Unit Abbreviation Equivalents
drops gtts —
teaspoon Tsp, Tsp, t 60 drops (depending on the size of the dropper and the viscosity of the medication)
tablespoon tbsp, Tbsp, tbs, T 36 inches, 3 feet
ounce oz 2 tbsp or 6 tsp
cup C, c 8 oz
pint pt 2 c, 16 oz
quart qt 2 pt, 4 c, 32 oz
gallon gal 4 qt, 8 pt, 16 c, 128 oz
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 9
Solving for Unknown Household Measures Using
Proportion
2 feet 1½ inches = ? inches
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 10
Solving for Unknown Household Measures Using
Fractions and Cross-Multiplication
2 feet 1½ inches = ? inches
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Metric System of Measurement
• Most common• Based on units of 10• Prefixes denote multiples (e.g., deci- is 1/10 the base, deka- is 10 times the base)
• Expressed as Arabic numerals preceding abbreviations (e.g., 10 mg)
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 12
Metric System of Measurement (cont’d.)
Units Weight Volume LengthBasic unit gram (G, g, gm, GM) liter (L, l) meter (M, m)
1000 units kilogram (kg, kG) kiloliter kilometer (km)
100 units hectogram* hectoliter hectometer
10 units dekagram dekaliter dekameter
1/10th unit decigram deciliter decimeter
1/100th unit centigram centiliter centimeter (cm)
1/1000th unit milligram (mg, mG) milliliter (ml, mL)
millimeter (mm)
1/1,000,000th unit
microgram (mcg) microliter micrometer (mcm)
*The measurements found in tialics are those that are not commonly used in calculating pharmaceutical dosages in heights, weights, or volumes. Measurements with abbreviations are those that are commonly used in pharmacology.
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 13
Equivalents in the Metric System
Type of Substance Abbreviation
Unit of Measure
Common Equivalents
Volume/Liquid L, l liter 1000 mL, 1000 cc
mL, ml, cc milliliter, cubic centimeter*
0.001 L
Weight G, g, gm, Gm gram 1000 mg, 0.001 kG
kG, kg kilogram 1000g
mG, mg milligram 0.001 gm, 1000 mcg
mcg microgram 0.000001 gm, 0.001 mg
Length M, m meter 100 cm, 1000 mm
cm centimeter 0.01 m, 10 mm
Mm millimeter 0.001 m, 0.1 cm
*A cubic centimeter (cc) is another way to express a milliliter. A cubic centimeter is the amount of space that is required to hold a milliliter of liquid.
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 14
Calculating Metric System Equivalents
1.2 L = ____ mL
5 mg = ____ g
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Converting Metric Measures Using the Mnemonic
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 16
Converting Metric Measures Using the Mnemonic (cont’d.)
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Apothecary System of Measurement
• Least common• Expressed as abbreviations preceding:• Lowercase Roman numerals with overhead
lines, for quantities under 10• Arabic numerals, for quantities over 10,
except 20 and 30
• Based on minim for volume and grain for weight. • Minims are not used today and only a few
medications are measured in grains, such as, nitroglycerin and aspirin.
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 18
Equivalents in the Apothecary System
Type of Substance Abbreviation
Unit of Measure
Common Equivalents
Volume/Liquid minim —
fl fluid dram ix (60)
fl fluid ounce viii (8)
Mass gr grain —
dram gr ix (60)
ounce viii (8)
# pound xii (12)*
*Note that in the apothecary system a pound is only 12 ounces.
Elsevier items and derived items © 2007 by Saunders, an imprint of Elsevier Inc Slide 19
Converting Apothecary Measures
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Summary
• Three common measurement systems• Household• Metric• Apothecary
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