GPhC Exam: preparing for the calculation questions

GPhC Pre-Reg Exam Preparation Specialists

Become familiar with the assessment

There will be some pre-registration pharmacy students that will squirm at the thought of the calculations assessment, whereas others deem this to be reasonably straightforward. With calculation-based questions, it would be ideal to get lots of practice so that you are introduced to as many question topics/styles as possible.

In your day-to-day role as a pharmacist, you may not have to complete a lot of the calculations that will be in the exam. Also, you may not spend much time on them during your working hours as a pre-registration student. Thus, it is crucial that you spend sufficient time to study and understand the calculation elements, as you will not be simply regurgitating facts; if you understand the theory behind a pharmaceutical calculation, you should be able to identify whether your final answer to a question makes sense or not.

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What are some of the key topics covered in this part of the assessment?

You will have 40 questions that need to be completed in 2 hours. A lot of students will believe they need to dedicate 3 minutes per question, though this is not necessarily true. Some questions may be completed within less than a minute, while other calculations will be a little more challenging, with various steps involved hence, require some more time.

You should have come across the different elements in the assessment during your university years. It is wise to refer back to your MPharm material during your revision. The following indicates majority of the topics that you should expect in the examination.

  • Doses and dose regimens
  • Dosage and unit conversions e.g. converting from mg to ml in a bottle
  • Estimations of kidney function e.g. Cockcroft-Gault equation
  • Displacement volumes and values e.g. reconstitution of antibiotic suspensions
  • Concentrations e.g. % w/v, % v/v
  • Dilutions e.g. c1v1 = c2v2
  • Molecular weight e.g. calculating the weight of an element in a solution
  • Using provided formulae e.g. body surface area, body max index
  • Infusion rates
  • Pharmacokinetics e.g. half-life, loading dose, maintenance dose.
  • Health economics e.g. number needed to treat, benefit-to-cost ratio
  • Quantities to supply e.g. number of tablets needed to sync items on a prescription

Although the calculations assessment is separate to Part 2 of the exam, remember that the second assessment may have a/some question(s) that will require some form of calculation.

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Group/partner work: create exam Q&As

As mentioned previously, there is no doubt that practicing past GPhC exam papers is very beneficial – as the saying goes, “practice makes perfect” – however, some individuals may fall into the pit by memorising the questions and answers, instead of mastering the technique of breaking down a question and how to answer a specific type of calculation.

It may be beneficial to devise your own calculations and work in a pair/group. Hand your questions to another person, and you can answer the calculation questions that they have devised. Thereafter, you can go through the methods and answers together.

This is great way to have discussions as you will often find that there is more than one way of reaching the correct answer. As we are all different, our minds work differently, and we may tackle mathematics in a different way to other people. As a result, you may pick up a few skills from your peers which will be of use in the exam.


There is some information that you simply have to know, and you possibly will not be provided with any clues in the exam question. One of the key aspects to memorise will be the colour of warfarin tablets to the correct strength of the tablet. For such details, you may want to create your own mnemonics to aid your revision such as the following example:

Wendy                0.5mg               White

Brings                1mg                  Brown

Blue                   3mg                  Blue

Plimsoles         5mg                  Pink

Learn units

Knowing how to get from one unit to another (e.g. grams to milligrams, millilitres to litres, etc) can be very simple. Some questions may use a specific unit throughout the question, and hence you would use the same units in your calculation method however, the question may finally ask you to present your answer as a different unit. Create small posters, stick little post-it notes on your laptop, or write down conversions on the inner side of your books/folders. If this is something you struggle with, ensure to prioritise the memorisation of it as it makes things much easier for you.

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