6 Common Units in Nursing
Learning Outcomes
By the end of this chapter, learners will be able to:
- identify common units of measurement for amount, mass and liquid volume in the metric system, and
- identify the correct abbreviations for common units of measure.
Understanding the Metric System
Types of Units
It’s likely you have learned about the metric system (also known as The International System of Units) at some point in your past education, but perhaps some of the details are a little fuzzy. There are seven basic types of measure, which relate to quantities of time, length, mass, electric current, thermodynamic temperature, amount of substance and luminous intensity (National Institute of Standards and Technology, 2020). However, we will focus on only four types, as they are the measurements most commonly used in nursing. The mole, grams, metres and litres. Respectively, these units measure amount of a substance, mass (weight), length and volume (capacity).
Difference Between Volume and Capacity
You might think of litres as a way to measure the volume of a liquid, but it’s not the most precise definition. Volume is a measure of how much space an object takes up, always measured in cubic units, such as cubic centimetres. Can you remember calculating the volume of objects in high school geometry? Multiplying the height, width and length of an object would give the volume of the object. Capacity is the measurement of how much of a substance can be inside an object, which could be matter existing in any state. Although there are many units to measure capacity, litre is most commonly used unit for measuring liquid matter. For use in nursing work, litre is commonly referred to as a measure of volume.
Base Units and Sizes of Measurements
When units of measure go up and down in size, they do so by a power of ten. A prefix is added to the base unit to indicate the size of the unit. For instance, a unit ten times larger than a gram is a decagram. You will not often see all of the possible units of measure being used in nursing work, so for the purposes of this text we will focus on the units you will use most often.
| Metric Prefix | Symbol | Power of 10 | Meaning | Multiply By |
|---|---|---|---|---|
| tera | T | 1012 | one trillion | 1,000,000,000,000 |
| giga | G | 109 | one billion | 1,000,000,000 |
| mega | M | 106 | one million | 1,000,000 |
| kilo | k | 103 | one thousand | 1,000 |
| hecto | h | 102 | one hundred | 100 |
| deca | da | 101 | ten | 10 |
| deci | d | 10−1 | one tenth | 1/10 |
| centi | c | 10−2 | one hundredth | 1/100 |
| milli | m | 10−3 | one thousandth | 1/1,000 |
| micro | μ | 10−6 | one millionth | 1/1,000,000 |
| nano | n | 10−9 | one billionth | 1/1,000,000,000 |
| pico | p | 10−12 | one trillionth | 1/1,000,000,000,000 |
Commonly Used Units
The following table outline units which are commonly used in medication orders and in medication administration in Canada. You should understand what these units measure and how to convert from one unit of measure to another. Occasionally, you will see measurements given using the US customary system of measure, derived from the British imperial system of measure. You may need to convert between units of the metric and imperial systems of measurement. Refer to the conversion table in this textbook for commonly used conversion factors.
| Quantity | Abbreviation | Measure |
|---|---|---|
| Amount | i.u. | international unit |
| Amount | mEq | milliequivalent |
| Amount | mmol | millimole |
| Volume | mL | millilitre |
| Volume | L | litre |
| Mass | mcg | microgram |
| Mass | mg | milligram |
| Mass | g | gram |
| Mass | kg | kilogram |
| Length | cm | centimetre |
| Length | m | metre |
Defining Units[1]
Within the table above, each unit of measure is defined in the glossary of this textbook. Click on the word to view the definition if you are unable to define the unit of measure in your own words. If using this book in another format, you can find the glossary at the back of the book.
Practice Set 6.1: Unit Abbreviations
Practice Set 6.1: Unit Abbreviations
- National Institute of Standards and Technology. (2020, January). SI units. https://www.nist.gov/si-redefinition/definitions-si-base-units ↵
A quantity of a substance that produces a particular effect, as agreed on though the international standard.
One thousandth of an equivalent, which is an amount of substance that reacts with a particular amount of hydrogen ions.
One thousandth of a mole.
One thousandth of a litre.
A metric measurement of volume equivalent to one thousand cubic centimetres.
One millionth of a gram.
One thousandth of a gram.
One thousandth of a kilogram.
The standard international unit for mass.
One hundredth of a metre.
The standard international unit for length.
