The basic unit of weight in the metric system
the gram. NOTE: The abbreviation for gram
The basic unit of volume in the metric system
the liter, abbreviated 1.
The basic linear unit of the metric system is
the meter, abbreviated m.
By using the prefixes deka, hecto, and kilo for
multiples often, one hundred, and one thousand
basic units, and the prefixes micro, mini, centi,
and deci for one ten thousandth, one thousandth,
one hundredth, and one tenth, you have the basic
structure of the metric system. By applying the
appropriate basic unit to the scale of figure 8-1,
you can readily determine its proper terms. For
instance, using the gram as the basic unit of
weight, we can readily see that 10 g would be 1
dekagram, 100 g would equal 1 hectogram, and
1000 g are called a kilogram. Conversely, going
down the scale, 0.1 g is then called a decigram,
0.01 g a centigram, and 0.001 g is called a
milligram. NOTE: In the metric system, no units
or their abbreviations are capitalized.
THE APOTHECARY SYSTEM
Although fast becoming obsolete, the
apothecary system is still used and must be taken
into consideration. It has two divisions of
measurement: weight and volume. The basic unit
of weight is the grain, abbreviated gr, and never
capitalized; and the basic unit of volume is the
THE AVOIRDUPOIS SYSTEM
This system is the one used in the United States
for weight only and is used in commercial buy-
ing and selling. The pound as we know it when
going to the market is the 16-ounce pound of the
avoirdupois system. The basic unit of the avoir-
dupois system is also the grain.
TABLE OF WEIGHTS AND
Table 8-1 is a table of weights and measures;
it should be thoroughly studied and memorized.
CONVERTING WEIGHTS AND
Occasionally there are times when it will be
necessary to convert weights and measures from
one system to another, either metric to apothecary
Figure 8-1.Metric system.
or vice versa. Since patients can hardly be expected
to be familiar with either system, always translate
the dosage directions on the prescription into a
household equivalent that they understand.
Therefore, the household measurements are
standardized, assuming that the utensils are com-
mon enough to be found in any home. Table 8-2
is a table of household measures, with their metric
and apothecary equivalents.
Table 8-2.Table of metric doses with approximate
8 - 3