Pharmacy Conversion Chart
Conversions and calculations are a daily part of working in a pharmacy. Being able to calculate the necessary pharmacy conversions is an important skill for anyone working in that environment.
This is particularly true with anyone dealing with working out dosages and dispensing medicine. Pharmacists and pharmacy technicians should be able to read a prescription and give the patient the right dosage and instructions.
What are Pharmacy Conversions?
As a pharmacy technician or pharmacist, you’ll often have to convert the dosage strength or quantity of medication when filling out a prescription.
You’ll typically convert from one unit of measurement to the other. To successfully convert these units of measurement, you need to know the correct methods of calculation. This is where a pharmacy conversion chart can be helpful.
What is a pharmacy conversion chart?
This is a helpful chart that has all common pharmacy conversions listed. Referring to this chart can help technicians convert the necessary values.
Why is a pharmacy conversion chart important?
It’s important to commit the common conversions and formulas to memory so that you can accurately dispense the required dosages and medicines.
You need to know what the prescribed dose is so that you know how much medicine to dispense. Giving a patient the wrong dosage could lead to serious harm or fatal errors. It’s just as important to give the patient the right dosage as it is to give them an adequate supply.
Ideally, both the pharmacist and pharmacy technician should have a good grasp of the different pharmacy conversions and values. A pharmacy technician who isn’t well versed might slow down workflow and create more work for everyone.
You can always print out a pharmacy conversion chart to keep on your person for added security or until you’ve committed it to memory.
The Most Important Pharmacy Measurement Conversions
Here are a few commonly used conversions that you should learn first.
Volume measurement conversions
15 drops gtt = 1 milliliter (mL)
1 teaspoon = 5 mL
1 tablespoon = 15 mL
1 liquid ounce = 30 mL
1 cup = 8 liquid ounces = 236.5 mL
1 pint = 16 liquid ounces = 473 mL
1 quart = 2 pints = 946 mL
1 liter = 1000 mL
1 gallon (4 quarts) = 3785 mL
Weight measurement conversions
1000 microgram (mcg) = 1milligram
1 Grain (Gr) = 65 mg
15 gr = 1 gram (g)
1 ounce (oz) = 28.4 g
1000 g = 1 kilogram (kg)
1 pound (lb) = 454 g
2.2 lbs = 1 kg
Measuring using “grain” is outdated, but you might still come across it from time to time. Also, note that 1 liquid ounce is not the same as 1 ounce.
FAQs
Which pharmacy conversions do I need to know for the PTCB test?
These following conversions are the ones that’ll come up on your PTCB test at some point. Make sure that you memorize them in preparation.
1 kilogram = 1,000 grams
1 kilogram = 2.2 pounds
1 liter = 1,000 milliliters
1 gram = 1,000 milligrams
1 milligram = 1,000 micrograms
1 grain = 64.8 milligrams
1 ounce = 28.35 grams
1 teaspoon = 5 milliliters
1 tablespoon = 15 milliliters
1 pound = 454 grams
Final Thoughts
Make sure you learn your pharmacy measurement conversions before you take your exam because they’re sure to come up. This knowledge is also necessary to be successful in your career in pharmacy.
https://ptceprep.com/pharmacy-conversion-chart/
https://www.drugs.com/article/measurement-conversions.html
https://ptcbtestprep.com/ptcb-math-know-your-conversions/
https://www.pharmacytimes.com/view/a-technicians-guide-to-measurement-conversions
What a pharmacy conversion chart covers
A pharmacy conversion chart lists the measurements pharmacists and pharmacy technicians use every day. These include metric units, apothecary units, and household units. Knowing how they relate to each other helps you read prescriptions accurately and prepare the right dose.
If you are thinking about a career in pharmacy, you will use these conversions from your first day of school. Pharmacy programs test this material early. Patients depend on it being right.
Metric units
The metric system is the standard in most pharmacy settings. You will see three main units: grams (g) for weight, liters (L) for volume, and meters (m) for length. Prefixes change the size of the unit. The most common ones are:
- Kilo (k): 1,000 base units
- Milli (m): one-thousandth of a base unit
- Micro (mc or µ): one-millionth of a base unit
So 1 gram equals 1,000 milligrams. One liter equals 1,000 milliliters. These two conversions come up constantly in pharmacy practice.
Household units
Patients at home often measure with spoons and cups. You need to translate those into metric amounts so labels and instructions are clear. The key household-to-metric conversions are:
- 1 teaspoon (tsp) = 5 milliliters (mL)
- 1 tablespoon (tbsp) = 15 mL
- 1 fluid ounce (fl oz) = 30 mL
- 1 cup = 240 mL
- 1 pint = 473 mL
- 1 quart = 946 mL
- 1 gallon = 3,785 mL
A common error is assuming a tablespoon equals 20 mL. It does not. Keeping the chart handy prevents that mistake.
Apothecary units
The apothecary system is an older set of measurements. You will not see it as often in modern pharmacy, but it still appears on some older prescriptions and in certain compounding settings. The most useful apothecary conversions are:
- 1 grain (gr) = 64.8 milligrams (mg), often rounded to 65 mg
- 1 dram = 3.888 grams (g)
- 1 ounce (apothecary) = 31.1 grams
The grain is the one you are most likely to see. Aspirin and thyroid medications were historically measured in grains.
Weight conversions used in pharmacy
Weight conversions matter for two main reasons. First, you calculate doses based on a patient’s weight. Second, you measure drug amounts when compounding or verifying a product.
Metric weight conversions
- 1 kilogram (kg) = 1,000 grams (g)
- 1 gram (g) = 1,000 milligrams (mg)
- 1 milligram (mg) = 1,000 micrograms (mcg)
Pounds to kilograms
Patient weights in the United States are usually recorded in pounds. Drug doses are usually calculated in milligrams per kilogram. So you convert pounds to kilograms first.
- 1 pound (lb) = 0.454 kilograms (kg)
- 1 kilogram (kg) = 2.2 pounds (lb)
To convert a patient’s weight, divide pounds by 2.2. For example, a patient who weighs 154 pounds weighs 70 kilograms.
Volume conversions used in pharmacy
Volume conversions come up when you prepare liquid medications. They also appear on prescription labels when you tell a patient how much to take.
Metric volume conversions
- 1 liter (L) = 1,000 milliliters (mL)
- 1 deciliter (dL) = 100 mL
Converting fluid ounces and milliliters
Most liquid prescriptions in the United States use milliliters on the label, but some older references still use fluid ounces. Knowing both helps you verify that a prescription makes sense.
- 1 fluid ounce = 29.57 mL, rounded to 30 mL in most pharmacy calculations
- 4 fluid ounces = 120 mL
- 8 fluid ounces = 240 mL (one cup)
- 16 fluid ounces = 473 mL (one pint)
Temperature conversions in pharmacy
Some medications must be stored at a specific temperature. Storage labels may use Fahrenheit (°F) or Celsius (°C), depending on the manufacturer. You need to read both.
How to convert between Fahrenheit and Celsius
To go from Celsius to Fahrenheit: multiply by 1.8, then add 32.
To go from Fahrenheit to Celsius: subtract 32, then divide by 1.8.
A few reference points you will use often:
- Room temperature: 68 to 77°F (20 to 25°C)
- Refrigerator: 36 to 46°F (2 to 8°C)
- Freezer: -4 to 14°F (-20 to -10°C)
- Body temperature: 98.6°F (37°C)
Many biologics, such as insulin and some vaccines, require refrigerator storage. A temperature error can make a medication ineffective or unsafe.
Roman numerals on prescriptions
Some prescriptions still use Roman numerals for quantities. This is more common with controlled substances and with older prescribers. You should be able to read the most common ones quickly.
- I or i = 1
- V or v = 5
- X or x = 10
- L = 50
- C = 100
When a smaller numeral appears before a larger one, you subtract. So IV = 4 and IX = 9. When a smaller numeral appears after a larger one, you add. So VI = 6 and XI = 11.
Common pharmacy abbreviations tied to conversions
Conversion charts often appear alongside prescription abbreviations. Understanding both together helps you read a prescription as a whole. Some abbreviations relate directly to units of measure.
- g: gram
- mg: milligram
- mcg or µg: microgram
- mL: milliliter
- L: liter
- tbsp: tablespoon (15 mL)
- tsp: teaspoon (5 mL)
- fl oz: fluid ounce (30 mL)
- gr: grain
- kg: kilogram
- lb: pound
- °C: Celsius
- °F: Fahrenheit
These abbreviations appear in pharmacy technician exams, in pharmacist licensure exams, and in clinical practice. Learning them now saves time later.
How conversions are tested in pharmacy programs
Pharmacy programs at both the technician and pharmacist level test conversion math heavily. You will see it in your first pharmacy math course. You will also see it on the PTCE (Pharmacy Technician Certification Exam) and the NAPLEX (North American Pharmacist Licensure Examination).
What pharmacy technician programs cover
Pharmacy technician programs, which usually take six months to two years to complete, include a full unit on pharmaceutical calculations. That unit covers metric conversions, household conversions, dose calculations, and ratio-and-proportion problems. Programs often give you timed calculation exercises so you build speed.
What PharmD programs cover
A Doctor of Pharmacy (PharmD) is a four-year professional degree that follows two to four years of undergraduate study. Conversions are part of the first-year curriculum. You build on them in pharmacokinetics (the study of how the body absorbs and removes a drug), compounding labs, and clinical rotations.
Ratio and proportion: the method behind the math
Most pharmacy calculation problems use one of two approaches: ratio-and-proportion or dimensional analysis (also called the factor-label method). Both rely on the conversion values in a pharmacy chart.
Ratio-and-proportion example
Say a medication is available as 250 mg per 5 mL, and the dose ordered is 500 mg. Set up the proportion like this:
250 mg / 5 mL = 500 mg / X mL
Cross-multiply: 250X = 2,500. Divide: X = 10 mL.
The patient gets 10 mL. This kind of calculation takes seconds once you practice it. The key is having the right conversion value at the start.
Dimensional analysis example
Dimensional analysis chains conversions together so the unwanted units cancel out. If you need to convert 2 grams to milligrams, you write:
2 g × (1,000 mg / 1 g) = 2,000 mg
The grams cancel, leaving milligrams. You can chain as many conversions as you need in one line.
Pediatric and geriatric dosing considerations
Weight-based dosing is more common in children than in adults. A dose might be ordered as 10 mg per kilogram per day. You convert the child’s weight from pounds to kilograms, then multiply. Getting the weight conversion wrong leads to a dosing error.
For older adults, kidney and liver function change how the body processes medication. Pharmacists sometimes adjust doses based on kidney function scores. Those scores also involve calculations that start with basic unit conversions.
Preparing for a pharmacy career
Conversion math is one part of a broader skill set you will build in a pharmacy program. You will also learn drug names, dispensing procedures, pharmacy law, and patient counseling. Pharmacy technician programs prepare you to support a pharmacist in a retail, hospital, or specialty setting. A PharmD program prepares you to practice as a licensed pharmacist and take on clinical responsibilities.
Both paths start with the same foundational math. Getting comfortable with a pharmacy conversion chart early gives you a real advantage when course work and exams begin.
If you are ready to take the next step, search accredited pharmacy technician and PharmD programs that match your schedule, location, and goals. Comparing programs side by side helps you find the right fit before you apply.