Percentage Solutions Calculator
Convert between % w/v, % w/w, % v/v and absolute drug amounts. Solve any of weight, volume, or strength.
Calculate the percentage concentration of a solution (w/v, v/v, or w/w).
grams of solute per 100 mL of solution
Formula
Drug amount (g or mL) = (Strength × Volume) ÷ 100
% w/v: g of solute per 100 mL of solution. % w/w: g per 100 g. % v/v: mL per 100 mL.
Step-by-step method
- 1
Identify the percentage type
Confirm whether the strength is w/v, w/w, or v/v — the units of the answer depend on which.
- 2
Read the strength and volume
Strength is the % value; volume (or mass) is the size of the solution.
- 3
Apply the formula
Drug = (Strength × Volume) ÷ 100. % w/v gives grams; % v/v gives millilitres; % w/w gives grams per 100 g.
- 4
Convert units if needed
Convert grams to milligrams or kilograms, or millilitres to litres, to match the prescription.
- 5
Cross-check
Sanity-check by inverting: would the calculated mass dissolved in the stated volume give the original percentage?
Worked example
Scenario: How many grams of glucose are in 500 mL of 5% w/v glucose?
Answer: (5 × 500) ÷ 100 = 25 g.
Practice calculations for the CRA
500+ exam-style calculation questions with detailed explanations, mapped to the GPhC Common Registration Assessment Part 1.