NurseQuizAI
Dosage Calculation Practice Problems for Nursing Students
Most nursing programs make you pass a med math exam, often at 90 to 100%, before you can give medications in clinical. The problems are not hard maths, but one slip with a decimal point is a medication error.
Work these practice problems with a calculator, then open the answer to see the full set-up. Every problem uses the same method: desired over have, times quantity. For a timed, interactive quiz, try our dosage calculation practice test.
What dosage calculation exams test
- Tablets and capsules: how many to give
- Oral liquids and injections: how many mL
- Weight-based doses in mg/kg, including lb to kg conversion
- IV infusion rates in mL/hr
- Manual drip rates in gtt/min using the drop factor
- Heparin and other unit-based infusions
8 dosage calculation practice questions with rationales
Answer each one before opening the rationale. Every option is explained, including the wrong ones.
- 1 tablet
- 2 tablets
- 2.5 tablets
- 0.5 tablet
Show answer and rationale
Answer: B
A. One tablet gives only 250 mg.
B. Correct. 500 mg ÷ 250 mg × 1 tablet = 2 tablets.
C. Would give 625 mg.
D. Would give 125 mg; the ratio is inverted.
- 0.5 tablet
- 1 tablet
- 2 tablets
- 0.25 tablet
Show answer and rationale
Answer: A
A. Correct. 0.125 mg ÷ 0.25 mg = 0.5 tablet.
B. Would give 0.25 mg, double the order.
C. Would give 0.5 mg, four times the order.
D. Would give 0.0625 mg.
- 2.5 mL
- 5 mL
- 10 mL
- 20 mL
Show answer and rationale
Answer: C
A. Would give 62.5 mg.
B. Would give 125 mg, half the order.
C. Correct. 250 mg ÷ 125 mg × 5 mL = 10 mL.
D. Would give 500 mg.
- 0.4 mL
- 2.5 mL
- 4 mL
- 0.04 mL
Show answer and rationale
Answer: A
A. Correct. 4 mg ÷ 10 mg × 1 mL = 0.4 mL.
B. This is have over desired, inverted.
C. Would give 40 mg, a tenfold overdose.
D. Decimal error; gives 0.4 mg.
- 150 mg
- 300 mg
- 660 mg
- 30 mg
Show answer and rationale
Answer: B
A. Uses 10 kg; 44 lb is 20 kg.
B. Correct. 44 lb ÷ 2.2 = 20 kg; 20 kg × 15 mg/kg = 300 mg.
C. Multiplied pounds by 15 without converting to kg.
D. Arithmetic error.
- 80 mL/hr
- 100 mL/hr
- 125 mL/hr
- 150 mL/hr
Show answer and rationale
Answer: C
A. Would deliver 640 mL in 8 hours.
B. Would deliver 800 mL in 8 hours.
C. Correct. 1,000 mL ÷ 8 hr = 125 mL/hr.
D. Would deliver 1,200 mL in 8 hours.
- 21 gtt/min
- 31 gtt/min
- 42 gtt/min
- 125 gtt/min
Show answer and rationale
Answer: B
A. Arithmetic error.
B. Correct. 1,000 mL × 15 gtt/mL ÷ 480 min = 31.25, rounded to 31 gtt/min.
C. Would need a drop factor of 20.
D. This is the mL/hr rate, not drops per minute.
- 10 mL/hr
- 20 mL/hr
- 40 mL/hr
- 50 mL/hr
Show answer and rationale
Answer: B
A. Would deliver 500 units/hr.
B. Correct. Concentration is 25,000 ÷ 500 = 50 units/mL; 1,000 units/hr ÷ 50 units/mL = 20 mL/hr.
C. Would deliver 2,000 units/hr.
D. This is the concentration in units/mL, not a rate.
How to get every dosage calculation right
- Use one method every time: (desired ÷ have) × quantity. Mixing methods causes errors under pressure.
- Convert units before you calculate: lb to kg (÷ 2.2), g to mg (× 1,000), mg to mcg (× 1,000).
- Ask whether the answer makes sense. More than 3 tablets, or more than 3 mL for an IM injection, usually means a mistake.
- Leading zero always (0.4 mL), trailing zero never (4 mg, not 4.0 mg).
- Know your program's rounding rules; drip rates round to whole drops.
Frequently asked questions
Desired dose divided by the dose you have on hand, multiplied by the quantity it comes in: (D ÷ H) × Q. Dimensional analysis gives the same answer with the units written out.
Total volume in mL multiplied by the drop factor in gtt/mL, divided by the time in minutes. Round to a whole drop.
Many programs require 90 to 100%, often with limited retakes, because a calculation error in practice is a medication error.