Free ATI TEAS 7 Mathematics guide
October 2026 - Measurements & Unit Conversions Study Guide for nursing students in
You need the household and metric conversions and the relationships between them: 1 kg is about 2.2 lb, 1 inch is 2.54 cm, 1 L is about 1.06 quarts. Convert in single, checkable steps, and divide pounds by 2.2 to reach kilograms — multiplying instead is the most common error in the whole section.
The conversions worth memorising
These are the ones that actually appear. Approximate values are marked, because the exam uses them.
| From | To | Factor |
|---|---|---|
| 1 kilogram | pounds | ≈ 2.2 lb |
| 1 inch | centimetres | 2.54 cm |
| 1 litre | quarts | ≈ 1.06 qt |
| 1 pound | ounces | 16 oz |
| 1 foot | inches | 12 in |
| 1 gallon | quarts / pints / cups | 4 qt / 8 pt / 16 cups |
| 1 teaspoon / tablespoon | millilitres | ≈ 5 mL / ≈ 15 mL |
| 1 hour | minutes / seconds | 60 min / 3,600 s |
The metric system is powers of ten
Within metric, every conversion is a decimal point moved. Learn the prefixes and you never need a factor table.
- kilo- 1,000 times the base unit. 1 kg = 1,000 g.
- centi- one hundredth. 100 cm = 1 m.
- milli- one thousandth. 1,000 mL = 1 L, and 1,000 mg = 1 g.
- micro- one millionth. 1,000 mcg = 1 mg.
- Larger unit to smaller: multiply. Smaller to larger: divide.
Converting with the units written in
Worked example
A patient weighs 176 lb. The dose is 2 mg per kilogram of body weight. What dose is required?
- Convert pounds to kilograms. Since a kilogram is heavier than a pound, the number must get smaller:
176 ÷ 2.2 = 80kg. - Sanity-check the direction. Multiplying would have given 387 kg, which is not a plausible body weight.
- Apply the rate:
80 kg × 2 mg/kg = 160mg. The kilograms cancel, leaving milligrams — the unit asked for.
160 mg. Writing the units into the multiplication is what confirms the setup: if they do not cancel to leave the unit you want, the conversion is inverted.
Before converting, decide whether the number should get bigger or smaller. Going to a smaller unit means more of them, so the number grows; going to a larger unit means fewer, so it shrinks. That one check catches an inverted conversion faster than redoing the arithmetic.
Multi-step conversions
When there is no direct factor, chain the steps and keep each one simple. Gallons to millilitres, for instance: gallons to quarts (×4), quarts to litres (÷1.06), litres to millilitres (×1,000).
Do them one at a time and write the intermediate value down. Combining three factors into one expression is where sign and place-value errors get in.
Terms to know
- Metric system
- A decimal system of measurement based on powers of ten.
- Household units
- Everyday non-metric units: teaspoons, cups, pounds, inches.
- Conversion factor
- The ratio relating two units, such as 2.54 cm per inch.
- Dimensional analysis
- Multiplying by conversion factors arranged so unwanted units cancel.
- Mass
- How much matter something contains — measured in grams and kilograms.
- Volume
- How much space something occupies — millilitres, litres, cups.
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.
Convert this weight from pounds to kilograms.
Divide by 2.2. The number must come out smaller.
How many millilitres are in this many litres?
Multiply by 1,000 — metric conversions are decimal shifts.
A dose is X mg per kg. What dose for this patient?
Convert to kilograms first, then multiply. Check the units cancel.
Which of these measurements is the largest?
Convert them all to one unit before comparing.
Key points
- Divide pounds by 2.2 for kilograms; multiplying is the classic error.
- Metric conversions are decimal shifts: kilo 1,000, centi 1/100, milli 1/1,000.
- Larger unit to smaller, multiply. Smaller to larger, divide.
- Decide whether the number should grow or shrink before you calculate.
- Chain multi-step conversions one step at a time, writing each value down.
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
A patient weighs 143 lb. What is this in kilograms, to the nearest whole number?
Show the answer and explanation
Correct answer: A. 65 kg
143 ÷ 2.2 = 65. Multiplying by 2.2 gives 315 kg, which the plausibility check rules out immediately; 71 kg comes from halving, a rough approximation that is not accurate enough here; and 145 kg treats the units as nearly interchangeable. -
Question 2 of 4
How many millilitres are in 2.5 litres?
Show the answer and explanation
Correct answer: C. 2,500 mL
A litre is 1,000 mL, so
2.5 × 1000 = 2,500. Moving to a smaller unit means a larger number, which rules out the first two, and 25,000 shifts the decimal one place too far. -
Question 3 of 4
A dressing measures 6 inches across. What is that in centimetres?
Show the answer and explanation
Correct answer: B. 15.24 cm
6 × 2.54 = 15.24. Centimetres are smaller than inches, so there must be more of them — which rules out 2.36 cm, the result of dividing instead of multiplying. 12 cm doubles the inches and 60 cm multiplies by ten. -
Question 4 of 4
Which of these is the largest volume?
Show the answer and explanation
Correct answer: D.
1/2gallonHalf a gallon is 8 cups, roughly 1.9 L, far ahead of the rest. In millilitres the others are 750, 800 and about 710, so they cluster together — which is exactly why converting everything to one unit before comparing is the only safe method here.
Put this TEAS topic into practice
Build a set on measurements and units and use the rationale on every question to reinforce what you just reviewed.
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