Percentage means parts per hundred or the
expression of fractions with denominators of 100.
Thus, a 10 percent solution may be expressed as 10%,
10/100, 0.10, or 10 parts per 100 parts.
It is often necessary for the pharmacist to
compound solutions of a desired percentage strength.
Percentage in that respect means parts of active
ingredient per 100 parts of total preparation.
Following are the three basic rules to remember in
solving percentage problems:
1. To find the amount of the active ingredient
when the percentage strength and the total
quantity are known, multiply the total weight
or volume by the percent (expressed as a
1 fl dr
2 fl dr
4 fl dr
(½ fl oz)
8 fl dr
(1 fl oz)
2 fl oz
4 fl oz
8 fl oz
16 fl oz
32 fl oz
*Official U.S.P. teaspoonful is 5 ml.
Table 6-2.Table of Metric Doses with Approximate Equivalents
for Weights and Liquid Measures
1 grain = 0.065 gram or 65 milligrams
1 gram = 15.432 grains
1 milliliter = 16.23 minims
1 fluid ounce = 29.57 milliliters
Table 6-3.Conversion Table for Weights and Liquid
Examples of Weight and Liquid Conversions
gr to g
gr/15.432 = g
ml to fl oz
ml/29.57 = fl oz
minims to ml
minims/16.23 = ml
mg to gr
mg/65 = gr
g to gr
g x 15.432 = gr
fl oz to ml
fl oz x 29.57 = ml
ml to minims
ml x 16.23 = minims
gr to mg
gr x 65 = mg
Table 6-4.Examples of Weight and Liquid Conversions
Example: Substance X contains 38% fat. How many
grams of fat are required to prepare 120 g of substance X?
Solution: 38% is expressed as a decimal fraction
(0.38) and multiplied by the amount of the finished
45.60 g , the weight of fat needed.