Calculating Drug Dosages: A Patient-Safe Approach | Dosage
Calculation Competency Review | 2026/2027
Institutional Nursing Skills Assessment — 50 Practice Questions with Verified Answers and Evidence-
Based Rationales
Section 1: Foundational Math — Fractions, Decimals & Rounding
1. A nurse is calculating a medication dose and needs to multiply 3/4 by 2/3. What is the product?
A. 1/2 B. 6/12 C. 5/7 D. 6/7
Correct Answer: A. 1/2
Rationale: Multiply numerators: 3 × 2 = 6. Multiply denominators: 4 × 3 = 12. The product is 6/12, which simplifies
to 1/2 by dividing both numerator and denominator by 6. Understanding fraction multiplication is essential for dosage
calculations involving fractional tablets (Pickar & Abernethy, Clinical Calculations, 9th ed.).
2. A nurse calculates a liquid medication volume as 2.46 mL. Applying standard rounding rules for mL, the nurse
should administer how many mL?
A. 2.4 mL B. 2.5 mL C. 2.46 mL D. 3 mL
Correct Answer: B. 2.5 mL
Rationale: For liquid medication volumes in mL, round to one decimal place. The digit in the second decimal place is
6, which is ≥ 5, so round up: 2.46 → 2.5 mL. Standard rounding rules: tablets round to the nearest whole (or half if
scored), mL to one decimal, and gtt/min to the nearest whole number (ISMP Guidelines for Safe Medication Practices).
3. A nurse needs to evaluate this expression using order of operations: 10 + 6 ÷ 2 × 3 − 4. What is the result?
A. 14 B. 15 C. 20 D. 18
Correct Answer: B. 15
Rationale: Following PEMDAS: first perform division and multiplication left to right. 6 ÷ 2 = 3, then 3 × 3 = 9. Now
substitute: 10 + 9 − 4 = 15. Order of operations is critical in multi-step dosage calculations to avoid medication errors
(Joint Commission NPSG.01.01.01).
4. A medication bottle states the concentration is 0.8% solution. If the total volume is 250 mL, how many grams
of the active drug are in the solution?
A. 0.8 g B. 2.0 g C. 20 g D. 200 g
Correct Answer: B. 2.0 g
Rationale: A 0.8% solution means 0.8 g per 100 mL. For 250 mL: 0.8 g/100 mL × 250 mL = 2.0 g. Alternatively, 0.008
× 250 = 2.0 g. Percentage concentration calculations are fundamental for IV admixtures and compounding (Pickar &
Abernethy, Clinical Calculations).
5. A nurse is calculating a dose and gets a result of 14.7 tablets. Which action should the nurse take first?
A. Administer 15 tablets since the number is close B. Stop and re-evaluate the calculation because 14.7
tablets is not reasonable
, C. Administer 14 tablets and discard the remainder D. Split 14 tablets in half and give 14.5 tablets
Correct Answer: B. Stop and re-evaluate the calculation because 14.7 tablets is not reasonable
Rationale: Any calculated dose exceeding 3–4 tablets should prompt immediate recalculation and verification. A result
of 14.7 tablets is a clear red flag indicating a potential error — the nurse should never administer this dose without
rechecking the order, concentration, and calculation. Estimation and reasonableness checking are essential safety
practices (ISMP High-Alert Medication List).
Section 2: Measurement Systems & Unit Conversions
6. A physician orders 0.25 g of amoxicillin. The pharmacy supplies amoxicillin 250 mg capsules. How many
capsules should the nurse administer?
A. 1 capsule B. 2 capsules C. 0.5 capsule D. 4 capsules
Correct Answer: A. 1 capsule
Rationale: First convert 0.25 g to mg: 0.25 g × 1,000 = 250 mg. The capsule strength is 250 mg, so 250 mg ÷ 250
mg/capsule = 1 capsule. Always convert to the same unit before calculating. The metric conversion factor is 1 g =
1,000 mg (Pickar & Abernethy, Clinical Calculations, 9th ed.).
7. A patient weighs 165 lb. Convert this weight to kilograms (round to one decimal place).
A. 33.0 kg B. 75.0 kg C. 79.5 kg D. 82.5 kg
Correct Answer: B. 75.0 kg
Rationale: To convert pounds to kilograms, divide by 2.2: 165 lb ÷ 2.2 = 75 kg. This conversion factor (1 kg = 2.2 lb)
is the most commonly used in clinical practice for weight-based dosing calculations. Always round kg to one decimal
place for medication dosing (Joint Commission).
8. A nurse needs to convert 1.5 L to milliliters for an IV fluid order. How many mL is this?
A. 15 mL B. 150 mL C. 1,500 mL D. 15,000 mL
Correct Answer: C. 1,500 mL
Rationale: To convert liters to milliliters, multiply by 1,000: 1.5 L × 1,000 = 1,500 mL. The metric conversion factor is
1 L = 1,000 mL. This conversion is essential for programming IV infusion pumps (Pickar & Abernethy, Clinical
Calculations, 9th ed.).
9. A patient is instructed to take 3 tsp of liquid medication at home. How many mL should the patient take per
dose?
A. 3 mL B. 10 mL C. 15 mL D. 30 mL
Correct Answer: C. 15 mL
Rationale: The household-to-metric conversion is 1 tsp = 5 mL. Therefore, 3 tsp × 5 mL/tsp = 15 mL. Common
household equivalents: 1 tsp = 5 mL, 1 Tbsp = 15 mL, 1 oz = 30 mL, 2 Tbsp = 1 oz. These conversions are critical for
patient education about home medication administration (ATI Nursing Education).
10. A nurse must convert a dose of 7,500 mcg to milligrams. What is the equivalent in mg?
A. 0.075 mg B. 0.75 mg C. 7.5 mg D. 75 mg
Correct Answer: C. 7.5 mg
Calculation Competency Review | 2026/2027
Institutional Nursing Skills Assessment — 50 Practice Questions with Verified Answers and Evidence-
Based Rationales
Section 1: Foundational Math — Fractions, Decimals & Rounding
1. A nurse is calculating a medication dose and needs to multiply 3/4 by 2/3. What is the product?
A. 1/2 B. 6/12 C. 5/7 D. 6/7
Correct Answer: A. 1/2
Rationale: Multiply numerators: 3 × 2 = 6. Multiply denominators: 4 × 3 = 12. The product is 6/12, which simplifies
to 1/2 by dividing both numerator and denominator by 6. Understanding fraction multiplication is essential for dosage
calculations involving fractional tablets (Pickar & Abernethy, Clinical Calculations, 9th ed.).
2. A nurse calculates a liquid medication volume as 2.46 mL. Applying standard rounding rules for mL, the nurse
should administer how many mL?
A. 2.4 mL B. 2.5 mL C. 2.46 mL D. 3 mL
Correct Answer: B. 2.5 mL
Rationale: For liquid medication volumes in mL, round to one decimal place. The digit in the second decimal place is
6, which is ≥ 5, so round up: 2.46 → 2.5 mL. Standard rounding rules: tablets round to the nearest whole (or half if
scored), mL to one decimal, and gtt/min to the nearest whole number (ISMP Guidelines for Safe Medication Practices).
3. A nurse needs to evaluate this expression using order of operations: 10 + 6 ÷ 2 × 3 − 4. What is the result?
A. 14 B. 15 C. 20 D. 18
Correct Answer: B. 15
Rationale: Following PEMDAS: first perform division and multiplication left to right. 6 ÷ 2 = 3, then 3 × 3 = 9. Now
substitute: 10 + 9 − 4 = 15. Order of operations is critical in multi-step dosage calculations to avoid medication errors
(Joint Commission NPSG.01.01.01).
4. A medication bottle states the concentration is 0.8% solution. If the total volume is 250 mL, how many grams
of the active drug are in the solution?
A. 0.8 g B. 2.0 g C. 20 g D. 200 g
Correct Answer: B. 2.0 g
Rationale: A 0.8% solution means 0.8 g per 100 mL. For 250 mL: 0.8 g/100 mL × 250 mL = 2.0 g. Alternatively, 0.008
× 250 = 2.0 g. Percentage concentration calculations are fundamental for IV admixtures and compounding (Pickar &
Abernethy, Clinical Calculations).
5. A nurse is calculating a dose and gets a result of 14.7 tablets. Which action should the nurse take first?
A. Administer 15 tablets since the number is close B. Stop and re-evaluate the calculation because 14.7
tablets is not reasonable
, C. Administer 14 tablets and discard the remainder D. Split 14 tablets in half and give 14.5 tablets
Correct Answer: B. Stop and re-evaluate the calculation because 14.7 tablets is not reasonable
Rationale: Any calculated dose exceeding 3–4 tablets should prompt immediate recalculation and verification. A result
of 14.7 tablets is a clear red flag indicating a potential error — the nurse should never administer this dose without
rechecking the order, concentration, and calculation. Estimation and reasonableness checking are essential safety
practices (ISMP High-Alert Medication List).
Section 2: Measurement Systems & Unit Conversions
6. A physician orders 0.25 g of amoxicillin. The pharmacy supplies amoxicillin 250 mg capsules. How many
capsules should the nurse administer?
A. 1 capsule B. 2 capsules C. 0.5 capsule D. 4 capsules
Correct Answer: A. 1 capsule
Rationale: First convert 0.25 g to mg: 0.25 g × 1,000 = 250 mg. The capsule strength is 250 mg, so 250 mg ÷ 250
mg/capsule = 1 capsule. Always convert to the same unit before calculating. The metric conversion factor is 1 g =
1,000 mg (Pickar & Abernethy, Clinical Calculations, 9th ed.).
7. A patient weighs 165 lb. Convert this weight to kilograms (round to one decimal place).
A. 33.0 kg B. 75.0 kg C. 79.5 kg D. 82.5 kg
Correct Answer: B. 75.0 kg
Rationale: To convert pounds to kilograms, divide by 2.2: 165 lb ÷ 2.2 = 75 kg. This conversion factor (1 kg = 2.2 lb)
is the most commonly used in clinical practice for weight-based dosing calculations. Always round kg to one decimal
place for medication dosing (Joint Commission).
8. A nurse needs to convert 1.5 L to milliliters for an IV fluid order. How many mL is this?
A. 15 mL B. 150 mL C. 1,500 mL D. 15,000 mL
Correct Answer: C. 1,500 mL
Rationale: To convert liters to milliliters, multiply by 1,000: 1.5 L × 1,000 = 1,500 mL. The metric conversion factor is
1 L = 1,000 mL. This conversion is essential for programming IV infusion pumps (Pickar & Abernethy, Clinical
Calculations, 9th ed.).
9. A patient is instructed to take 3 tsp of liquid medication at home. How many mL should the patient take per
dose?
A. 3 mL B. 10 mL C. 15 mL D. 30 mL
Correct Answer: C. 15 mL
Rationale: The household-to-metric conversion is 1 tsp = 5 mL. Therefore, 3 tsp × 5 mL/tsp = 15 mL. Common
household equivalents: 1 tsp = 5 mL, 1 Tbsp = 15 mL, 1 oz = 30 mL, 2 Tbsp = 1 oz. These conversions are critical for
patient education about home medication administration (ATI Nursing Education).
10. A nurse must convert a dose of 7,500 mcg to milligrams. What is the equivalent in mg?
A. 0.075 mg B. 0.75 mg C. 7.5 mg D. 75 mg
Correct Answer: C. 7.5 mg
