The Basics: Metric System
Conversion of units requires the use of a “conversion factor,” which is any equivalent equation in which the known and the unknown units are involved (Tables 3.1–3.4) (Bill 2000). You must set up a proportion of values on either side of the equation.
Cross-multiply and divide.
50 pounds = 22.7 kg
Table 3.1. Weight.
| Unit | Fraction | Symbol |
| Kilogram | 1000 grams | kg |
| Gram | 1000 milligrams | g |
| Milligram | 1/1000 of a gram | mg |
| Microgram | 1/1,000,000 of a gram | μcg or μg |
Table 3.2. Weight.
Table 3.3. Volume.
Table 3.4. Common unit conversions.
| 1 kilogram | = | 2.2 pounds |
| 1 teaspoon | = | 5 mL |
| 1 tablespoon | = | 15 mL |
| 1 grain | = | 60 mg |
Percentages
Percent can be expressed as “out of 100” or “for every 100.” For example: 25% can be written as
The decimal point can be moved two places to the left to achieve the same calculation.
Agent strength as percent solution
Agents with the dose listed as a concentration percent represent grams in 100 mL.
Lasix as a 5% solution has a concentration of 50 mg/mL.
Lidocaine as a 2% solution has a concentration of 20 mg/mL.
The decimal point can be moved one place to the right in any percent solution to discern the mg/mL concentration.
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