Selected abbreviations are listed below.
| Abbreviation | Unit of measurement |
|---|---|
| g | gram |
| gal. | gallon |
| gr | grain |
| kg | kilogram |
| lb | pound |
| M or min | minim |
| mcg | microgram |
| mg | milligram |
| mL | milliliter |
| oz | ounce |
| pt | pint |
| qt | quart |
| tbsp | tablespoon |
| tsp | teaspoon |
Other common abbreviations used in the medical field:
| Abbreviation | Meaning |
|---|---|
| a.a. | of each |
| a.c | before meals |
| b.i.d. | twice a day |
| c. | with |
| gtt. | drop, drops |
| h.s. | at bedtime |
| o.d. | right eye |
| o.s. | left eye |
| p.c. | after meals |
| p.r.n. | as needed |
| q.i.d. | four times a day |
| t.i.d. | three times a day |
| u.d. | as directed |
1 fluid ounce = 30 milliliters
One liter of pure water weighs approximately one kilogram so 1cc (mL) of water weighs 1 gram.
"A spoonful" generally means heaped or rounded, with as much above the bowl of the spoon as in the spoon. However, a measure of liquid is a level spoonful.
| Apothecary measurement | Metric equivalent |
|---|---|
| 1 gallon | 3800 mL |
| 1 gallon | 128 fluid oz |
| 1 quart | 960 mL |
| 1 quart | 32 fluid oz |
| 1 pint | 480 mL |
| 1 pint | 16 fluid oz |
| 4 fluid oz | 120 mL |
| 8 fluid oz | 240 mL |
| 10 minims | 0.6 mL |
| 15 minims | 1 mL |
1 teaspoonful = 5 milliliters
1 tablespoonful = 15 milliliters
1 ounce = 30 grams
1 gram = 15 grains
| Apothecary measurement | Metric equivalent |
|---|---|
| 2 oz | 60 g |
| 4 oz | 120g |
| 16 oz | 1 lb |
| 1/200 gr | 300 mcg |
| 1/150 gr | 400 mcg |
| 1/100 gr | 600 mcg |
| 1gr | 60 mg |
| 7 ½ gr | 500 mg |
| 10 gr | 600 mg |
In 1866, the United Stated Congress legalized the use of the metric system within the United States. The law also established approximate equivalents between customary and metric measurements.
1 gram = 1,000 milligrams
1 milligram = 1,000 micrograms
| Apothecary measurement | Metric equivalent |
|---|---|
| 0.05 mg | 50 mcg |
| 0.5 mg | 500 mcg |
| 5 mg | 5,000 mcg |
| 0.05 g | 50 mg |
| 0.5 g | 500 mg |
| 5 g | 5,000 mg |
Note: Exact equivalents are used for compounding and calculations requiring a high degree of accuracy.
International units: An old measurement of vitamin activity determined by biological methods as opposed to new measures that are determined by direct chemical analysis.
An international unit is quantity of a biologic (such as a vitamin) that produces a particular biological effect agreed upon as an international standard. Many health foods and supplements still use i.u. (IU).
| Apothecary measurement | Metric equivalent |
|---|---|
| 1 g | 15.43 gr |
| 1 mL | 16.23 minims |
| 1 minim | 0.06 mL |
| 1 gr | 64.8 mg |
| 1 pint (pt) | 473.2 mL |
| 1 oz | 28.35 g |
| 1 lb | 453.6 g |
| 1 kg | 2.2 lb |
| 1 qt | 946.4 mL |
| 0.1 mg | 1/600 gr |
| 0.12 mg | 1/500 gr |
| 0.15 mg | 1/400 gr |
| 0.2 mg | 1/300 gr |
| 0.3 mg | 1/200 gr |
| 0.4 mg | 1/150 gr |
| 0.5 mg | 1/120 gr |
| 0.6 mg | 1/100 gr |
| 0.8 mg | 1/80 gr |
| 1 mg | 1/65 gr |
A grain is a unit of weight in the U.S. Customary System.
The apothecaries' system of mass is an obsolete system formerly used by apothecaries (now called pharmacists or chemists) in English-speaking countries. Sometimes "ap" is added to the front of the unit to identify it as part of the apothecaries' system.
During the first half of the 20th Century, the apothecaries' system was replaced by the metric system.
| Apothecary measurement | Metric equivalent |
|---|---|
| 1/4 grain | 15 mg |
| 1/2 grain | 3 mg |
| 1 grain | 60 mg |
| 11/2 grains | 90 mg |
| 5 grains | 300 mg |
| 10 grains | 600 mg |
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.