1. Medical Dosage Calculations A Dimensional Analysis Approach
Eleventh Edition
Chapter 4
The Household and Metric Systems

2. Learning Objectives
4.1 Identify the units of measurement in the household and metric systems. 4.2 Recognize the abbreviations for the units of measurement in the two systems. 4.3 State the equivalents for the units of volume. 4.4 State the equivalents for the units of weight. 4.5 State the equivalents for the units of length. 4.6 Convert from one unit to another within each of the two systems.
Slide 2 is list of textbook LO numbers and statements

3. The Household System (1 of 5)

4. The Household System (2 of 5)
Alert
Because the volume of ordinary household spoons, cups, or glasses may vary, some of the equivalences in the following Table are only approximate.

5. The Household System (3 of 5)
Table 4.1 Household Equivalents of Liquid Volume
1 quart (qt) =
2 pints (pt)
1 pint (pt)
2 measuring cups
1 measuring cup
8 ounces (oz)
1 ounce (oz)
2 tablespoons (T)
1 tablespoon (T)
3 teaspoons (t)

6. The Household System (4 of 5)
Table 4.2 Household Equivalents of Weight
1 pound (lb) =
16 ounces (oz)

7. The Household System (5 of 5)
Table 4.3 Household Equivalents for Length
1 foot (ft) =
12 inches (in)

8. The Household System Example 4.1 (1 of 3)
The prescriber directs the patient to take 2 ounces of a laxative agent, citrate of magnesia, whenever necessary. How many tablespoons would the patient take?
2 oz = ? T

9. The Household System Example 4.1 (2 of 3)
You want to cancel the ounces and obtain the equivalent amount in tablespoons.

10. The Household System Example 4.1 (3 of 3)
Therefore, 2 ounces is approximately the same as 4 tablespoons. The patient should take 4 tablespoons of citrate of magnesia whenever necessary.

11. The Household System Example 4.2
A patient drank 24 oz of the laxative agent COLYTE. How many glasses did the patient drink?

12. Weight in the Household System

13. Weight in the Household System Example 4.3 (1 of 4)
An infant weighs 8 pounds 11 ounces. What is the weight of the infant in ounces?
First, you need to change the 8 pounds to ounces.

14. Weight in the Household System Example 4.3 (2 of 4)
The equation would be
8 lb = ? oz
You want to cancel the pounds and obtain the equivalent amount in ounces.

15. Weight in the Household System Example 4.3 (3 of 4)

16. Weight in the Household System Example 4.3 (4 of 4)
Then, you would add the extra ounces.
128 oz + 11 oz = 139 oz
So, the 8-pound, 11-ounce infant weighs 139 ounces.

17. The Metric System (1 of 7)

18. The Metric System (2 of 7)
The metric system is the most widely used system of measurement in medical dosage calculation.

19. The Metric System (3 of 7) Table 4.4 Format of the Metric System Name
Kilo
hecto
deka
BASE UNIT
deci
centi
milli *
micro
Abbreviation K h da
g, L, m d c m mc
Multiple of the Base
1,000
100 10 1
0.1
0.01
0.001

20. The Metric System (4 of 7)
Table 4.5 Metric Prefixes Used in Dosage Calculation
Metric Prefixes
kilo
means
one thousand
(1,000 times the base)
centi
one hundredth
(0.01 times the base)
milli
one thousandth
(0.001 times the base)
micro
one millionth
( times the base)

21. The Metric System (5 of 7)
Table 4.6 Metric Equivalents of Liquid Volume
1 cubic centimeter (cc or cm3) =
1 milliliter (mL)
1,000 milliliters (mL)
1 liter (L)

22. The Metric System (6 of 7) Table 4.7 Metric Equivalents of Weight
1 kilogram (kg) =
1,000 grams (g)
1 gram (g)
1,000 milligrams (mg)
1 milligram (mg)
1,000 micrograms (mcg)

23. The Metric System (7 of 7) Table 4.8 Metric Equivalents of Length
1 centimeter (cm) =
10 millimeters (mm)

24. The Metric System Example 4.4 (1 of 2)
Convert 1,750 milliliters to an equivalent volume in liters?
For this example, to convert 1,750 milliliters to liters is a jump of 3 places to the left.

25. The Metric System Example 4.4 (2 of 2)
In 1,750 mL, move the decimal point 3 places to the left as follows:

26. The Metric System Example 4.5 (1 of 2)
Convert 4.5 kilograms to an equivalent amount in grams.
To convert kg to g, jump 3 decimal places to the right.

27. The Metric System Example 4.5 (2 of 2)
Move the decimal point 3 places to the right.

28. Chapter Summary (1 of 4)
The metric system is the dominant system used in health care.
It is important to memorize the equivalences between the various units of measurement of the household and metric systems.
It is important to memorize the abbreviations for the various units of measurement.
To convert units of measure in the metric system, use the shortcut method of moving the decimal point. Always jump 3 places except for cm-mm conversions, which use a 1 place jump.

29. Chapter Summary (2 of 4)
Memorize and Remember, each jump is 3 places in this chart:
kilogram
gram
milligram
microgram kg
g, L
mg, mL
mcg

30. Chapter Summary (3 of 4)
Abbreviations for units of measurement are not made plural by adding the letters.
Example: 70 mcg and 3 oz (not 70 mcgs and 3 ozs).
Insert a leading zero for decimal numbers less than 1.
Example: 0.05 g and 0.34 mL (not .05 g and .34 mL).
Omit trailing zeros for decimal numbers.
Example: 7.3 mL and 0.07 g (not 7.30 mL and g).

31. Chapter Summary (4 of 4) Numbers greater than 999 need commas.
Example: 2,500 mL and 20,000 mcg (not 2500 mL and mcg).
Leave space between the number and the unit of measurement.
Example: 60 mL and 100 g (not 60mL and 100g).
Avoid the use of fractions with metric units of measurement.