Free pharmacy calculators.

What these calculators are for

These are study aids, not clinical tools. They exist so you can learn a method, check your working and practise for an examination. They are not medical advice, they are not clinical decision support, and none of them should be used to make a decision about a real patient. Every result must be verified against your local formulary, the product literature and a qualified pharmacist before it goes anywhere near prescribing. The full position is set out in our medical disclaimer.

Why calculations are worth practising separately

Calculations behave differently from the rest of pharmacology. Mechanism knowledge builds slowly and holds for years, whereas calculation accuracy is a skill that decays without use and fails under time pressure rather than from ignorance. Most candidates who lose marks here understood the method perfectly well and mishandled a unit, a decimal place or a daily-versus-single dose distinction.

The arithmetic itself is universal, but the conventions are not. Units, expected precision, whether a calculator is permitted and whether answers are typed or chosen from options all vary between examinations, so practising in the format you will actually sit matters as much as practising the method. Our comparison of the five boards sets out how each one handles this.

Use them, then understand them

A calculator gives you an answer, not a reason. Knowing that a patient has a creatinine clearance of 62 mL/min only helps if you also know which drugs care about that number and why, which is the part these pages link out to. Start with how drug names tell you the mechanism or work through the free practice questions.

Which calculations are worth learning first?

Creatinine clearance, body surface area, alligation, dilution, ratio strength and infusion rates are the six that appear across every pharmacy licensing exam. Our guide to the twelve pharmacy calculations to master explains why those six repay drilling and why the remaining six, the corrections such as adjusted calcium and corrected phenytoin, are better understood than automated. If a calculation keeps going wrong for a reason you cannot name, the drug class pages usually hold the mechanism the number depends on.

Can I use these calculators in an exam?

No. Boards either ban calculators outright or permit only a basic one, so these are for learning the method and checking your working beforehand. The rules differ sharply: the GPhC Common Registration Assessment permits a calculator in its calculations paper and forbids one in the clinical paper, while other boards fold calculations into clinical items entirely. Our exam preparation hub sets out what each board allows.