Apothecary/metric equivalents

Abbreviations

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

Approximate Liquid Measures

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

Approximate Household Equivalents

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

Metric Conversions

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

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