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Chapter 3 Systems of Measurement and Weight
(kilometer), the number of units decreases. When you divide, the decimal
point moves to the left.
The four units of weight, or mass, are related to each other by a factor
of 1000. A kilogram is 1000 times larger than a gram. A gram is 1000 times
larger than a milligram, which is 1000 times larger than a microgram. The
same relationship is true for liters and milliliters; a liter is 1000 times larger
than a milliliter. Table 3-3 lists four of the most commonly used equivalent
measurements. Because they are so important to dosage calculations, you
should memorize them.
Table 3-3
Equivalent Metric Measurements
1 kg ⫽ 1000 g
1 mg ⫽ 1000 mcg
1 g ⫽ 1000 mg
1 L ⫽ 1000 mL
To convert a quantity from one unit of metric measurement to another:
To convert from a larger unit of measurement to a smaller unit of measurement, divide, which moves your decimal point to the left because it
multiply, which moves
has a lesser value.
your decimal point to
To convert from a smaller unit of measurement to a larger unit of meathe right.
surement, multiply, which moves your decimal point to the right because
it has a greater value.
divide, which moves
Figure 3-2 will help you determine both the direction and the number of
your decimal point to
places to move the decimal point when you convert between units of metthe left.
ric measurement. For example, as shown in figure 3-2, milliliter is three
places to the right of the basic unit of a liter.
Prefix
kilo-
hecto-
deca-
Base Unit
deci-
centi-
milli-
decimilli-
centimilli-
micro-
Value
1000
100
10
1
1
_
1
_
1
_
1
_
1
_
1
_
10
100
1000
10,000
100,000
1,000,000
Abbreviation
Value relation to
Base Unit
kg
gram
mg
mcg
kL
liter
mL
mcL
1000
100
10
1
0.1
0.01
0.001
0.0001
0.00001
0.000001
Figure 3-2 Metric System Place Values—To convert a quantity from liters (larger) to milliliters
(smaller), multiply by 1000 (which moves the decimal point three places to the right). Similarly, to
convert a quantity from grams (smaller) to kilograms (larger), divide by 1000 (which moves the
decimal point three places to the left).
EXAMPLE 1 ◗
Convert 4 L to milliliters (mL).
A milliliter (mL) is smaller than a liter (L); a quantity will have more milliliters than liters. Using Figure 3-2, you can see that there are 1000 milliliters in each liter. The number of units increases by a factor of 1000 and
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