Medication calculation requires you to know how to multiply and divide.
You’ll also need to know six metric measurements and five household measure-
ments (ounces, teaspoon, tablespoon, cup and drop).
Let’s begin with the metric system. The metric system uses grams to measure
weight and liters to measure volume as shown in Table 7-1. Prefixes are used to
indicate the number of grams and liters. Table 7-2 shows the commonly used
prefixes that you’ll see when calculating medication.
Each prefix indicates the value. The prefix is placed before the unit of mea-
sure such as 1 kilogram or 1 milliliter. Look at Kilo in Table 7-2. The factor is
1000, which is larger than a gram or liter. Therefore, you multiple the gram or
liter by 1000. That is, a kilogram is 1000 grams and a kiloliter is 1000 liters.
The important point to remember is that the prefix of the measure implies the
size of the measurement.(^114) CHAPTER 7 Dose Calculations
Unit Purpose Equivalents
Gram Weight 1 kilogram (kg) = 1000 grams (g)
1 gram (g) = 1000 milligrams (mg)
1 milligram = 1000 micrograms (mcg)
1 kilometer = 1000 liters
Liter Volume 1 liter (L) = 1000 milliliters (mL) =
1000 cubic centimeters (cc)
1 milliliter (mL) = 1 cubic centimeter (cc)
Table 7-1. Units and their equivalents.
Unit Purpose Equivalents
Kilo 1000 One thousand times
Centi 0.01 One hundredth part of
Milli 0.001 One thousandth part of
Micro 0.000001 One millionth part of
Table 7-2. Prefixes used in medication.