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RMIT University Library - Learning Lab

Nursing calculations


The following tutorials are an introduction to basic drug calculations for nursing. After each tutorial, test your knowledge with the interactive activities.

  • Finding the volume required

    What is volume required formula? This formula tells us how much liquid-form medication we need to give a patient, considering the strength they need and the source that it comes from. This tutorial introduces the Volume Required formula and shows you how to apply it to a problem.

  • Using proportions with liquid solutions

    If you need double the dose of medication, you need to give double the volume of the liquid that it is dissolved in and so on. This is the simple principle behind the Volume Required formula. Learn how you could solve these problems before applying the formula.

  • Converting between large and small units

    How do you convert between units? Nurses use units that begin with milli and micro a lot. If you express your dosage in a smaller unit, the number must get bigger, and vice versa. Find out how to convert dosages between larger and smaller units.

  • Medication dosage by body weight

    How do you deal with a unit like mg/kg? Milligrams per kilogram means that you must give a certain amount (mgs) of a drug for each kilogram of the patient’s body mass. Bigger patients need a bigger dose! Learn what this unit means and when and how to use it.  

  • The flow rate formula

    What does Flow Rate = Volume/time mean? Flow rate is determined by the volume of liquid that passes by (into a patient) within a certain time period. This is the fundamental formula for all IV problems.  

  • Managing fractions and decimals

    What do you do if the Flow Rate calculation involves fractions such as ¼ of an hour or 0.5 litres? Find out how this is managed mathematically.

  • Drop factor: converting between millilitres and drops

    Drops are just another unit for measuring the amount of fluid flowing into a patient’s system. Discover what ‘drop factor’ means, and how to convert between millilitres and drops. 

  • Converting flow rates between mL/hr and dpm

    How do you convert IV flow rates? In the previous video, we looked at converting between millilitres (ml) and drops. This time we are converting not only the volumes, (drops and mls) but the units for time as well. Find out how this is done.