1.Easy
Practice exercise (made-up values, not clinical guidance). 150 g of potassium chloride is dissolved in water to a total volume of 1000 mL. What is the percentage strength p (% w/v)?
150 g1000 mL
p = %
Pharmacy calculations worksheet with answers
2.Easy
A solution is 0.5% w/v. You need 19.5 mg of the drug. Draw up the volume in the syringe: what volume V is that?
0.5% w/v19.5 mg
V = mL
3.Medium
Practice exercise (made-up values, not clinical guidance). A vial of penicillin G contains 5 000 000 units. Its practice label gives three strengths (see the table). You add 3.2 mL of diluent. The prescribed dose is 750 000 units. What volume V do you draw up? Round to one decimal place.
3.2 mL → 1 000 000 units/mL750 000 units
V = mL
4.Medium
A solution has a ratio strength of 1:1000. You need 0.13 mg. Draw up the volume in the 1 mL syringe: what volume V is that?
1:10000.13 mg
V = mL
5.Hard
Practice exercise (made-up values, not clinical guidance). You must prepare 300 mL of 4% chlorhexidine from a 20% stock and purified water. How many mL V of water do you need? Round to the nearest whole mL.
20%0%4%300 mL
V = mL
6.Hard
A vial holds 250 mg of powder. You add 4.2 mL of diluent, and the powder adds 0.8 mL of volume. The prescription is 160 mg. Draw up the dose: what volume V do you give?
250 mg4.2 mL + 0.8 mL160 mg
V = mL
Answer key
- 1. p = 15 %
- 2. V = 3.9 mL
- 3. V = 0.8 mL
- 4. V = 0.13 mL
- 5. V = 240 mL
- 6. V = 3.2 mL
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