The mathematics employed in the daily practice is essentially basic arithmetic applied to critical medical calculations with a strong emphasis on unit conversion and the utilisation of ratios and proportions.

1. Calculations of Medication Dosages

Nurses accurately calculate the medication amount to be administered.

Ratios and Proportions – Applicable when desired dose and volume is known.
Weight-Based Dosing Calculating pediatric or critical-care medication doses ordered per kilogram This requires the patient’s weight in pounds (lbs) to be converted to kilograms (kg).
Titration: Calculation of variable doses, which may be adjusted based on the patient’s parameter.

2. Unit Conversions

Nurses are always, constantly changing measurements in their head to make sure that they are giving something accurately, especially between systems:

Metric System – Converting between metric units of weight and volume
Metric to Household/Apothecary – Conversion of patient weight in lbs to kg and fluid volume in ounces to milliliters

3. IV Flow Rate Calculations

Nurses must set the rate at which intravenous fluids or medications infuse:

Pump Rates – Calculating milliliters per hour.
Drip Rates Formula for determining drops per minute for infusions when an electric pump is not used.

4. Intake and Output (I&O)

Nurses need to calculate and document a patient’s total fluid intake and output during a shift; this requires frequent additions and subtractions of different volumes, and often converting household measures to milliliters to accurately chart.