GPhC calculation practice by topic

Part 1 of the Common Registration Assessment is 40 calculation questions in 2 hours. These ten guides each cover one calculation type with a short method, three original questions and worked answers. They are revision material, not GPhC questions.

• Dose by weight calculations for the GPhC assessment

  Three original questions on mg/kg dosing, with the working shown and the usual traps pointed out.

• Volume to give: liquid medicine calculations

  The most common Part 1 setup: a dose, a strength written as mg in some mL, and a volume to measure.

• Percentage strength calculations: w/v, w/w and ratios

  Three original questions on percentage and ratio strengths, converted to mg per mL before anything else.

• Dilution calculations with C1V1 = C2V2

  Three original dilution questions, each worked two ways so the answer can be checked.

• Infusion rate calculations in mL per hour

  Three original questions on volume over time, with the minutes-to-hours step shown every time.

• Drip rate calculations: drops per minute

  Three original questions that turn a volume and time into a whole number of drops per minute.

• Body surface area calculations

  Three original questions using the Mosteller equation, with a dose per m² step in two of them.

• Creatinine clearance (Cockcroft-Gault) calculations

  Three original questions using the Cockcroft-Gault equation with the constants given in the BNF.

• Moles and millimoles calculations

  Three original questions linking mass, molecular weight and concentration in mmol.

• Displacement volume calculations for reconstitution

  Three original reconstitution questions, each starting from the final volume.

Also see the formula sheet, the eight sample questions and the 15 free practice questions.