Free ATI TEAS 7 Mathematics guide
October 2026 - Choosing the Right Unit Study Guide for nursing students in
Choosing a sensible unit is its own skill: millilitres for a medication dose, litres for daily fluid intake, grams for a dressing, kilograms for a patient. The right unit is the one that produces a manageable number — neither 0.00004 nor 4,000,000.
Two questions decide it
- What kind of quantity is it? Length, mass, volume, time, temperature or area. Getting this wrong means an answer that is not just badly scaled but nonsensical — grams cannot measure a distance.
- What scale is it? Once the quantity is right, pick the unit that puts the figure between roughly 1 and 1,000.
The usual choices
| Measuring | Unit | Why |
|---|---|---|
| A patient's weight | kilograms | A typical adult is 50–120 — a workable range |
| A tablet's active ingredient | milligrams | Grams would give figures like 0.005 |
| A single medication dose | millilitres | Litres would give 0.005 L |
| Daily fluid intake | litres | Millilitres would give figures in the thousands |
| A wound | centimetres or millimetres | Metres would give 0.03 m |
| A corridor | metres | Centimetres would give figures in the hundreds |
| A journey | kilometres or miles | Metres would give tens of thousands |
| Body temperature | degrees Celsius | The scale medicine uses |
| A dressing or a swab | grams | Kilograms would give 0.004 kg |
Precision follows the unit. A patient's weight recorded to the nearest kilogram is sensible; a neonatal weight is recorded in grams because a kilogram is too coarse to be safe. Where the answer changes a decision, the unit has to be fine enough to carry it.
Choosing and checking
Worked example
Which unit should be used to record the amount of a drug in a single tablet, given a typical amount of 0.0005 of a gram?
- Identify the quantity: mass.
- Try grams:
0.0005 g— four leading zeros, easy to misread by a factor of ten. - Try milligrams:
0.5 mg— readable. - Try micrograms:
500 mcg— also readable, and the usual convention below 1 mg.
Micrograms, or milligrams if the figure stays at or above 1 mg. Grams is technically correct and practically unsafe, because a leading string of zeros is where decimal errors happen.
Common mismatches the exam offers
- A unit of the wrong quantity — millilitres for a weight, grams for a length.
- A unit three orders of magnitude out — kilograms for a tablet, millimetres for a corridor.
- A unit that is fine in principle but produces a figure nobody could read at a glance.
- An area answered in linear units, or a volume answered in square units.
Terms to know
- Unit
- The standard quantity a measurement is expressed in.
- Magnitude
- The scale of a value, in powers of ten.
- Precision
- How finely a measurement is recorded.
- Micrograms
- One thousandth of a milligram, written mcg. Used where milligrams would be a decimal.
- Square units
- The units of area, such as cm². Length units cannot express area.
What the TEAS asks most
The same core ideas appear in different wording. If you can answer these without stopping to think, you have what this section requires.
Which unit is most appropriate for measuring X?
The one that matches the quantity and yields a figure roughly between 1 and 1,000.
Which of these measurements is unreasonable?
The one whose unit is the wrong quantity, or whose magnitude is impossible for the thing described.
Which unit would a nurse use to record this?
Clinical convention: kilograms for weight, millilitres for volume, milligrams or micrograms for drug quantities.
Key points
- Match the quantity first — length, mass, volume, time, temperature, area.
- Then match the scale: aim for a figure between about 1 and 1,000.
- Millilitres for doses, litres for daily intake, kilograms for patients, milligrams for drug content.
- Below 1 mg, use micrograms rather than a decimal fraction of a milligram.
- Area takes square units; a length unit cannot express it.
Review quiz
4 questions on this topic, each with the reasoning worked through. Pick an answer to see how it went, or open the explanation straight away.
-
Question 1 of 4
Which unit is most appropriate for recording an adult patient's body weight?
Show the answer and explanation
Correct answer: B. Kilograms
Kilograms put an adult in the 50–120 range, which is readable and precise enough. Grams would give figures in the tens of thousands, milligrams in the millions, and millilitres measure volume rather than mass at all.
-
Question 2 of 4
Which of these measurements is unreasonable?
Show the answer and explanation
Correct answer: C. A single tablet weighing 5 kg
Five kilograms is roughly the weight of a small child, so it cannot describe a tablet — the unit is the right quantity but six orders of magnitude out. The other three are all ordinary clinical measurements at sensible scales.
-
Question 3 of 4
A drug is present at
0.00025grams per tablet. How is this best expressed?Show the answer and explanation
Correct answer: B.
0.25mg, or 250 mcgShifting from grams to milligrams gives
0.25mg, and to micrograms gives 250 mcg — both readable, with micrograms preferred below 1 mg. The original grams figure invites a decimal error, while 250 mg and0.25mcg are out by a factor of a thousand in each direction. -
Question 4 of 4
A nurse needs to record the area of a pressure sore. Which unit is appropriate?
Show the answer and explanation
Correct answer: B. Square centimetres
Area is two-dimensional, so it takes square units, and square centimetres are the right scale for a wound. Plain centimetres measure a single dimension, while millilitres and grams measure volume and mass.
Put this TEAS topic into practice
Build a set on identifying appropriate units of measurement and use the rationale on every question to reinforce what you just reviewed.
Keep reading
More TEAS Resources
Guides and tools across the TEAS course.
TEAS 7 Exam Prep
Format, sections, timing
TEAS 7 FAQ
Scoring, retakes, test day
Is the TEAS Hard?
An honest answer
How Long Is the TEAS 7?
209 minutes, section by section
What Is a Passing TEAS Score?
Your programme sets the bar
TEAS Reading
18 topics · 39 scored questions
TEAS Math
18 topics · 34 scored questions
TEAS Science
22 topics · 44 scored questions
TEAS English
21 topics · 33 scored questions
Free TEAS Practice Test
Sit a set before you buy
TEAS Plans & Pricing
Choose your access
Start TEAS Prep
Create your account
TEAS Study Guide
All four sections, free
8-Week Study Plan
Week-by-week schedule
TEAS Cheat Sheet
Formulas and high-yield facts
TEAS vs HESI A2
Which exam to take
