Crash Course: Dosage Calculations for Nurses

Dosage Calculations - Blog (1)Math is an inevitable reality of a career in nursing. Math problems and dosage calculations do not end once you leave nursing school. Because of this reality, it’s important that nurses keep their math skills sharp.

To help with that, we’ve put together a crash course on dosage calculations, complete with basic calculation information and links to practice problems!

Common Conversions

Here are a few common conversions every nurse should know. Memorizing these basic conversions will come in handy while on the job, and make your day run a little easier.

1 Liter = 1000 milliliters

1 gram = 1000 milligrams

1 milligram = 1000 micrograms

1 Kilogram = 2.2 pounds

This infographic from MedicTests can also be helpful in doing common conversions. Try doing a few of the example problems listed at the bottom of the graphic.1


Methods of Calculations

There are three methods that can be used to do drug calculations, according Nurses Are Great. Any one of these calculation methods will give you the same results. For all three methods, remember (D) is the dose ordered/desired, (H) is the dose on hand and (V) is the form and amount the drug comes in.2

  1. Basic Formula: This method of calculation requires you to divide the desired dose (D) by the dose on hand (H), then multiply that by the form or amount the drug comes in (V).2Screen Shot 2016-06-19 at 7.09.08 PM2. Ratio and Proportion: This method is the oldest method used in calculating dosages. The left side is the known quantities and the right side is the desired dose and amount to give. Multiply the extremes and the means.2Screen Shot 2016-06-19 at 7.14.13 PM Screen Shot 2016-06-19 at 7.14.18 PM
    3. Fractional Equation: This method requires you to cross multiply and solve for ‘x’ (‘x’ being what to give the patient.2Screen Shot 2016-06-19 at 7.15.49 PM

Practice Makes Perfect

The easiest way to get better at dosage calculations is to practice. While it may not sound like the most fun, practicing a few dosage calculations a day can really help keep you sharp on the job.

Caroline from EmpoweRN reminds us, “in real life you can’t get these problems wrong because one missed calculation can have very severe problems to your patient.”3

Nurses Are Great points out that practice makes perfect when it comes to nurse math. “Many nurses have difficulty with drug calculations. Mostly because they don’t enjoy or understand math. Practicing drug calculations will help nurses develop stronger and more confident math skills.”2

Here are a few links to dosage calculation practice problems, so you can brush up on your math skills:

Remember that the math you do as a nurse can have life changing impacts. It’s important as a nurse to feel confident in your math skills and make sure you know what you’re doing when completing dosage calculations.

How do you keep your math skills sharp as a nurse? Tell us in the comments below!