PTCB Guide to Unit Conversions – Strategy, Practice Questions & Key Units.

At a Glance.

• Unit conversions are foundational knowledge for pharmacy technicians. They are essential for calculating doses, preparing medications, and interpreting prescriptions accurately.
• The PTCB exam frequently tests conversions as part of dosage calculations, concentration calculations, compounding, and temperature.
• Most unit conversion questions involve the metric system, including grams, milligrams, micrograms, liters, and milliliters.
• Technicians should memorize the most common pharmacy conversions. These include 1 g = 1,000 mg, 1 kg = 2.2 lb, 1 tsp = 5 mL, and 1 tbsp = 15 mL.
• Always convert units before solving a calculation to avoid medication errors. Double-check your answer units at the end.
• Pay close attention to decimal points, especially when converting between grams, milligrams, and micrograms.
• Temperature conversions may also appear, particularly for medication storage requirements.
• Many PTCB conversion questions are presented in realistic pharmacy scenarios, requiring you to apply conversion skills in context.
• Double-check that your answer is reasonable before selecting it, as simple conversion errors can lead to incorrect doses.
• Regular practice is the best way to improve speed and accuracy on unit  conversion PTCB questions.

Why are conversions tested on the PTCB exam?

Medication conversions are tested on the PTCB exam because pharmacy technicians must accurately calculate and convert measurements when preparing, dispensing, and labeling medications. Even a small conversion error can result in an incorrect dose, making conversion skills essential for patient safety.

Conversions are tested primarily as part of the Order Entry and Processing knowledge domain of the exam.

Commonly tested conversions include:

• Metric units (mg, g, mcg, kg, mL, L)
• Household measurements (teaspoons, tablespoons, fluid ounces)
• Apothecary units (grains; though this is less likely to be tested)
• Temperature (°C and °F)
• Weight and volume (lb to kg, oz to mL)

Examples include converting:

• 1 g = 1,000 mg
• 1 mg = 1,000 mcg
• 1 kg = 2.2 lb
• 1 tsp = 5 mL
• 1 tbsp = 15 mL

For the PTCB exam, technicians are required to perform conversions quickly and accurately, as they are often incorporated into dosage calculations, compounding questions, as well as prescription interpretation. Understanding common conversion factors is considered a foundational skill for safe pharmacy practice.

Note: for more information on what math gets tested more broadly on the PTCB exam, consult our full PTCB math guide.

What are the most common PTCB conversion mistakes?

From our experience training pharmacy technicians, we have come across at least six common causes of conversion mistakes. Consider the following common causes:

• Confusing milligrams (mg) and micrograms (mcg): this is one of the most common mistakes. Remember that 1 mg = 1,000 mcg, so converting in the wrong direction can result in a 1,000-fold dosing error.
• Forgetting to convert units first: before performing any dosage calculation, ensure all measurements are in the same unit (e.g. convert grams to milligrams or pounds to kilograms). We always recommend our students to first check if any conversions are needed before proceeding to answer a question. And second to that, always double-check at the end if units are consistent.
• Mixing up teaspoons and tablespoons: A teaspoon (tsp) equals 5 mL, while a tablespoon (tbsp) equals 15 mL. Confusing the two can triple the intended dose.
• Using the wrong conversion factor: memorize common pharmacy conversions such as 1 kg = 2.2 lb and 1 oz = 30 mL. Avoid guessing during the exam, though educated guesses are an effective second-line resort.
• Moving the decimal point the wrong way: when converting between metric units, carefully determine whether you’re converting to a larger or smaller unit. A misplaced decimal can lead to a significant dosing error.
• Skipping a final reasonableness check: after completing a conversion, ask yourself whether the answer makes sense. For example, converting grams to milligrams should produce a larger number, while converting milligrams to grams should produce a smaller number. Always consider the logical validity of the answer you have produced. If necessary, double-check your answer process.

Remember – always convert units before performing any dosage calculation and double-check your decimal placement before selecting your answer. This simple habit can prevent most conversion-related errors.

Conversions that Get Tested.

Below we list the key unit conversions that pharmacy technicians are required to know. All conversions listed are considered examinable material on the PTCB test.

Category	Conversion	Equivalent
Weight	1 kilogram (kg)	1,000 grams (g)
	1 gram (g)	1,000 milligrams (mg)
	1 milligram (mg)	1,000 micrograms (mcg)
	1 grain (gr)	65 mg
	1 ounce (oz)	28.35 grams
Volume (Metric)	1 liter (L)	1,000 milliliters (mL)
	1 milliliter (mL)	1 cubic centimeter (cc)
Volume (Household)	1 teaspoon (tsp)	5 mL
	1 tablespoon (tbsp)	15 mL (3 tsp)
	1 fluid ounce (fl oz)	29.57 mL (approx. 2 tbsp’s)
	1 cup	240 mL
	1 pint (pt)	480 mL (16 fl oz)
	1 quart (qt)	960 mL (2 pt, 32 fl oz)
	1 gallon (gal)	3,840 mL (4 qt, 128 fl oz)
Length	1 inch (in)	2.54 centimeters (cm)
Temperature	°C to °F	(°C × 9/5) + 32
	°F to °C	(°F − 32) × 5/9
Misc Pharmacy	Percent (%) solution	g per 100 mL (e.g. 5% = 5 g / 100 mL)

Sample PTCB Conversion Questions.

Below, you can find ten sample PTCB conversion questions. These questions reflect the style and standard of conversion questions tested on the pharmacy technician exam.

Take a few moments to work through each question before comparing your answers / methodology with our answer explanation section directly below.

Question 1.

Convert 2.5 grams to milligrams.

a. 25 mg

b. 250 mg

c. 2,500 mg

d. 25,000 mg

Question 2.

A prescription calls for 1 teaspoon of cough syrup to be given to a child three times daily. How many milliliters should the patient receive per day?

a. 15 mL

b. 30 mL

c. 45 mL

d. 60 mL

Question 3.

Convert 0.7 liters to milliliters.

a. 0.7 mL

b. 70 mL

c. 700 mL

d. 7,000 mL

Question 4.

A pediatric patient weighs 56 pounds. What is the patient’s weight in kilograms?

a. 21.5 kg

b. 23.9 kg

c. 25.4 kg

d. 27.2 kg

Question 5.

Convert 3 ounces to milliliters.

a. 88.7 mL

b. 92.5 mL

c. 98.2 mL

d. 103.6 mL

Question 6.

A patient weighs 154 lb. The pharmacist asks you to calculate the patient’s weight in kilograms for dosing purposes. What is the weight of the patient?

a. 63 kg

b. 68 kg

c. 70 kg

d. 73 kg

Question 7.

A caregiver is instructed to administer 30 mL of cough syrup. How many tablespoons is this?

a. 1 tbsp

b. 2 tbsp

c. 2.5 tbsp

d. 3 tbsp

Question 8.

A child is prescribed 125 mcg of levothyroxine. However, the tablets are labeled in milligrams. How many mg was the child prescribed?

a. 0.0125 mg

b. 0.125 mg

c. 1.25 mg

d. 12.5 mg

Question 9.

A patient is instructed to apply 0.5 g of ointment per application. How many milligrams of ointment are applied each time?

a. 50 mg

b. 500 mg

c. 5,000 mg

d. 50,000 mg

Question 10.

A refrigerated drug must be stored at 2°C to 8°C. A technician checks the refrigerator and records the temperature as 41°F. What is 41°F in degrees Celsius?

a. 1 °C

b. 2 °C

c. 3 °C

d. 5 °C

Answer Explanations.

Answer to Question 1 – c. 2,500 mg

Given that there are 1,000 mg in 1 gram, we must multiply 1,000 mg x 2.5 grams to determine the correct answer.

Answer to Question 2 – a. 15 mL

One teaspoon contains 5 mL, therefore three teaspoons contain 15 mL.

Answer to Question 3 – c. 700 mL

There are 1,000 mL in 1 liter, therefore 0.7 L x 1,000mL = 700 mL.

Answer to Question 4 – c. 25.4 kg

There are 2.2 lbs in 1 kilogram. Therefore, we must divide 56 lbs / 2.2 to establish the weight of the patient in kilograms.

Answer to Question 5 – a. 88.7 mL

There are 29.57 mL in 1 ounce, therefore 3 ounces contains 88.7 mL.

Answer to Question 6 – c. 70 kg

The patient weighs 154 lbs.

As there are 2.2 lbs in 1 kilo: 154 lbs / 2.2 = 70kg.

Answer to Question 7 – b. 2 tbsp

There are 15 mL per tablespoon, therefore 2 tablespoons = 30 mL.

Answer to Question 8 – b. 0.125 mg

1 mg = 1,000 mcg

Therefore: 125 mcg / 1,000 = 0.125 mg

Answer to Question 9 – b. 500 mg

There are 1,000 mg in 1 gram.

Therefore: 0.5 g x 1,000 = 500 mg

Answer to Question 10 – d. 5 °C

Use the conversion formula: °C = (°F − 32) × 5/9

(41 − 32) × 5/9 = 5°C

Frequently Asked Questions.

What is the best way to remember unit conversions?

Everyone has their own preferred way, but we strongly recommend flashcards. Flashcards are a highly effective way of reviewing the key formulae in a fast and effective manner. In time, unit conversions become second nature.

I’m not motivated to learn conversions, or PTCB math generally. Any suggested ideas?

This is far more common than you might think! Many pharmacy technicians find math difficult – and understandably so.

One of the best ways to learn something that may not immediately strike a core interest is to remember why you are learning it. This is a foundational skill as a pharmacy technician to help prevent medication errors – and many medication errors are serious.

The shift of a decimal point can change a dose ten-times. Consider learning conversions and math from a professional perspective. That way it becomes more relevant and when something is more relevant to us, we are more likely to summon the interest to learn it.

What is the most effective way to prepare for PTCB math?

Practice questions.

The more exam-like practice questions you take, the faster you will become prepared and plug any knowledge gaps you may have. Study weaker topics more than stronger topics – and always identify specific steps where you went wrong. When structured, you will watch your progress develop fast.

You can also access our dedicated PTCB math module to help you master the math even faster.

What is the best strategy to adopt when faced with unit conversions?

Always identify unit conversions at the beginning of a question!

This is essential. Because by rectifying unit conversions at the beginning, it means you can work through the rest of the question in an accurate manner. Solving or identifying unit conversions in the middle of a question can create confusion. And at the very end, double-check your unit conversions to see if they are accurate.