Building the Basics: Estimation and Rounding

Estimation uses various mental maths methods to find approximate answers to problems and equations. Having good rounding and estimating skills will help you check answers quickly and efficiently in your head.

Nurses and healthcare professionals use estimation when a calculation for medications or intravenous therapy results in a number with decimal places. Whether the number is rounded to a whole number or to 1 or 2 decimal places will depend on the situation. Basic fluid infusion devices (“pumps”) can only be programmed to deliver milliliters (mL) per hour. It has to be a whole number. When drawing up liquid medication into a syringe, the amount is normally rounded to 1 decimal place if the syringe has appropriate calibration marks. For paediatric (children’s) doses, the volume of medication is usually rounded to 2 decimal places to ensure the most accurate dose of medication.

You can use estimation with addition, subtraction, multiplication and division equations, as well as with fractions, decimals and ratios.

When you talk about a number you have rounded, you usually use the word 'approximately', 'about' or 'roughly' to indicate it's not an exact answer. For example, 'the time is about 9:30' or 'it costs approximately $13'.


Note: It is important to estimate answers for calculations you make on a calculator (especially in a test situation) so you avoid basic mistakes. For example, thinking the answer to 9,000 X 3,100 is about 270,000 rather than roughly 27,000,000.