For students
Pediatric dosage calculation practice
Practice problems for nursing, pharmacy and medical students. The numbers are for arithmetic practice, not real doses.
Practice problems
Worked problems
1. Convert 33 lb to kg.
- 33 ÷ 2.2 = 15 kg
Answer: 15 kg
2. Order: 15 mg/kg per dose. Child weighs 12 kg. How many mg per dose?
- 15 × 12 = 180 mg
Answer: 180 mg
3. Order: 30 mg/kg/day divided every 12 hours. Child weighs 18 kg. How many mg per dose?
- 30 × 18 = 540 mg/day
- Every 12 hours = 2 doses
- 540 ÷ 2 = 270 mg
Answer: 270 mg
4. Give 240 mg. Stock is 160 mg/5 mL. How many mL?
- 160 ÷ 5 = 32 mg/mL
- 240 ÷ 32 = 7.5 mL
Answer: 7.5 mL
5. Order: 10 mg/kg per dose. Child weighs 44 lb. Stock is 100 mg/5 mL. How many mL?
- 44 ÷ 2.2 = 20 kg
- 10 × 20 = 200 mg
- 100 ÷ 5 = 20 mg/mL
- 200 ÷ 20 = 10 mL
Answer: 10 mL
6. Order: 0.5 mg. Stock is 250 mcg per mL. How many mL?
- 0.5 mg = 500 mcg
- 500 ÷ 250 = 2 mL
Answer: 2 mL
7. Order: 45 mg/kg/day divided every 8 hours. Child weighs 22 lb. Stock is 200 mg/5 mL. How many mL per dose?
- 22 ÷ 2.2 = 10 kg
- 45 × 10 = 450 mg/day
- 450 ÷ 3 doses = 150 mg
- 200 ÷ 5 = 40 mg/mL
- 150 ÷ 40 = 3.75 mL
Answer: 3.75 mL
8. A 16 kg child is ordered 40 mg every 6 hours. The safe range is 8-10 mg/kg/day. Is the order safe?
- 40 mg × 4 doses = 160 mg/day
- 160 ÷ 16 = 10 mg/kg/day
- 10 is within 8-10
Answer: Yes, at the top of the range
A method that works every time
- Convert the weight to kg (lb ÷ 2.2) and every amount to the same unit (mg or mcg).
- If the order is mg/kg, multiply by the weight. If it’s mg/kg/day, multiply, then divide by the number of doses.
- Divide the dose by the concentration (mg per mL) to get the volume.
- Check it: does the mL make sense for a child that size? Recalculate anything that surprises you.
The formulas page covers mg/kg, BSA and the Clark’s, Young’s and Fried’s rules.
Common questions
How do you round pediatric dosage calculation answers?
Follow your program’s rules. A common convention is to round mL to the nearest tenth (or hundredth for volumes under 1 mL) and to round only the final answer, not intermediate steps.
What is the formula for dosage calculations?
Desired ÷ have × quantity: dose ordered ÷ dose on hand × volume on hand. For weight-based orders, first multiply mg/kg by the weight in kg.
Are these real doses?
No. The numbers are chosen for arithmetic practice and don’t describe real medicines or real safe ranges.