Weights and Measures

for Pharmacy Technicians

This page discusses the Apothecaries System.

It's important to understand the different systems of weights and measures used when working in a pharmacy.

The Apothecaries' system is no longer as widely used as it once was, but it's still considered one of the standard systems of weights and measures.

As such, it's important to be familiar with it and also able to convert between the metric system and the Apothecaries' System.

When dealing with weight, the Apothecaries' system uses pounds, ounces, drachms, scruples and grains.

Here are the appropriate conversions within the Apothecaries' System:

1 pound = 12 ounces

1 ounces = 8 drachms

1 drachm = 3 scruples

1 scruple = 20 grains

As you can see, the first big difference is that a pound contains 12 ounces, instead of 16. Here are a few more conversions of various units within the Apothecaries' System:

1 pound = 96 drachms

1 ounce = 24 scruples

1 drachm = 60 grains

1 ounce = 480 grains

The easiest way to memorize the units is just to work with them a little bit. Pick a random unit and a random number and the break it down into the smaller units, and convert it up into larger units. If you picked 4 ounces for example:

4 ounces = 96 scruples

4 ounces= 1920 grains

4 ounces = 32 scruples

4 ounces = 1/3rd of one pound

For measurements of volume, the Apothecaries' System uses the following units: liquid pints, fluid ounces, fluid drams, fluid scruples and the minim.

1 liquid pint = 16 fluid ounces

1 fluid ounce = 8 fluid drams

1 fluid dram = 3 fluid scruples

1 fluid scruple = 20 minim

Aside from the pint once again being 16 ounces instead of 12, the rest of the units break down and convert at the same rate as the measure of weight. Again, the fastest way to learn and become familiar with these terms is to practice using them.

Here are the conversions from the Apothecaries' System to metric measurements:

1 pound = 373 grams

1 ounce = 31.1 grams

1 drachm = 3.89 grams

1 scruple = 1.296 grams

1 grain = 64.8 milligrams

1 liquid pint = 473 milliliters

1 fluid ounce = 29.6 milliliters

1 fluid dram = 3.7 milliliters

1 fluid scruple = 1.23 milliliters

1 minim = 0.062 milliliter

With a little patience and a bit of practice, it's easy to become familiar with the Apothecaries' System of weights and measurement.

Just remember that the pound has 12 ounces but the pint has 16 fluid ounces and the rest is pretty easy.

An ounce is always broken down into 8 drachms or drams(liquid) and the next step is into 3 scruples. And then the smallest unit is always 20 grains/minim to make a scruple.

Good luck and remember to always take the time to double check any conversions you make when working as a Pharmacy Technician.

Every measurement is important and it's worth taking the extra moment to ensure accuracy.

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