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Roman Numerals:

Rules:1. When a letter is repeated, its value is repeated2. A letter can not be repeated more than three times3. V, L, & D are never repeated4. When a smaller numeral is placed BEFORE a larger numeral,

its value is SUBTRACTED from the larger value

5. When a smaller numeral is placed AFTER a larger numeral, itsvalue is ADDED to the larger value

6. V, L, & D are never subtracted from larger digits7. Never subtract more than one numeral8. I is used before V and X only

X is used before L and C onlyC is used before C and D only

Metric System:Today, the metric system is the most commonly used measurement system forpharmaceutical calculations.

Basic Metric Units:Gram (g) weightLiter (l) volumeMeter (m) length

Prefix Symbol Meaning Conversion

Micro- mc or One millionth basic unit x 1,000,000

Milli- m One thousandth basic unit x 1,000

Centi- c One hundredth basic unit x 100

Deci- d One tenth basic unit x 10

Basic Unit (g, l, or m)Hecto- H One hundred times basic unit x 0.01

Kilo- K One thousand times basic unit x 0.001

I 1

V 5

X 10

L 50C 100

D 500

M 1000

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Apothecary System:The apothecary system is less common than the metric system, however somemedications are still prescribed using apothecary weights. The apothecarysystem has units of measure for weight and volume but none for length. Becausethe apothecary system and the metric system both have units of measure for

weight and volume, it is simple to convert these measurements from one systemto the other.

Unit of measure Conversion

Volume

Minim

Fluidram 60 minims

Fluidounce 8 fluidrams

Pint 16 fluidounces

Quart 2 pints (32 fluidounces)

Gallon 4 quarts (8 pints)Weight

Grain

Scruple 20 grains

Dram 3 scruples

Ounce 8 drams (24 scruples)

Pound 12 ounces

Avoirdupois System:

The avoirdupois system is a measurement system for weights only. The systemcontains three units of measure; two of which are commonly used in everydaylife, the pound and the ounce, and one which is rarely used outside thepharmacy, the grain.

Unit of Measure Conversion

Grain*

Ounce 437.5 grains

Pound 16 ounces

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Household Measurements:Household measurements are regularly used in pharmacy practice, as they areeasiest for the patients to understand.

Unit of Measure ConversionVolume

Teaspoonful (tsp)

Tablespoonful (Tbsp) 3 tsp

Fluid ounce * 2 tbsp

Cup 8 fluid ounces

Pint 2 cups

Quart 2 pints

Gallon 4 quarts

Weight

Ounce

Pound* 16 ounces

Intersystem ConversionsAs a pharmacy technician, it is essential that you are able to convertmeasurements within and between systems.

Volume:

16.23 minim= 1 ml1 fluidram= 5 ml = 1 teaspoonful1 teaspoonful= 5ml

1 tablespoonful= 15ml1 fluid ounce= 30 ml33.8 fluid ounces= 1 L1 pint= 16 fluid ounces= 480 ml1 quart= 2 pints= 960 ml1 gallon= 4 quarts= 3840ml

Weight:

1 grain= 65mg15.4 grains= 1g

1 ounce = 30 g1 ap pound= 5760 grains= 373.2 g1 av pound= 7000 grains= 454 g2.2 lbs= 1 kg