Understand the idea.
What are you measuring?
First name the quantity you want to measure. Length describes how long or far; mass describes how heavy; capacity describes how much a container can hold; temperature describes how hot or cold. Different quantities need different instruments.
Use a ruler for a straight length, scales for mass, a measuring jug for liquid volume and a thermometer for temperature. A measurement needs both a number and a unit: and describe different quantities.
Choose a useful metric unit
Choose a unit that suits the size. Millimetres and centimetres suit small lengths, while metres suit larger ones. Use grams or kilograms for mass, millilitres or litres for capacity, and degrees Celsius for temperature.
Check that the result is sensible for the object. A pencil could be long, but would be enormous. A drink bottle holding is plausible; would need a much larger container.
See the method in action.
Match object, instrument and unit
How would you measure the length of a workbook?
Worked solution
- 1
Identify the quantity.
The question asks how long a workbook edge is, so measure length.
- 2
Choose the instrument.
A ruler can be lined up with the straight edge of the workbook.
- 3
Choose and report a suitable unit.
Centimetres give a useful-sized measurement for a workbook; no actual length has been supplied.
Measure its edge with a ruler and report centimetres.
Compare units for capacity
A small medicine cup holds 20 of a metric liquid unit. Is 20 mL or 20 L sensible?
Worked solution
- 1
Identify the size of the container.
A medicine cup holds only a small amount of liquid.
- 2
Compare the units.
Litres are much larger units than millilitres, so 20 litres would be far too much for this cup.
- 3
Choose the sensible measurement.
Millilitres suit the small liquid capacity described.
20 mL.
Try it yourself.
Check your understanding
Which is a sensible mass for a school bag: 4 kg or 4 mL?
Show answer & reasoning
4 kg
Choose . Kilograms measure mass, which is the quantity needed for a school bag. Millilitres describe liquid volume or capacity, so cannot be its mass.
Keep practising
6 worksheet questions · 9 marks
Read the questions online
- Name the quantity measured by a thermometer.1 mark
- Choose a useful unit for a classroom's length: cm, m or °C.1 mark
- Choose a sensible capacity for a drink carton: 250 mL or 250 L.1 mark
- Match ruler, kitchen scales and measuring jug to length, mass and liquid amount.3 marks
- A learner writes that a pencil has a mass of 15 cm. Explain and correct the unit type.2 marks
- A parcel has a mass of 1000 g. Use to express its mass in kilograms.1 mark
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- Name the quantity measured by a thermometer.1 mark
A thermometer tells how hot or cold something is.
Temperature. - Choose a useful unit for a classroom's length: cm, m or °C.1 mark
It is a length.
Metres give a practical number for a room.
Metres (m). - Choose a sensible capacity for a drink carton: 250 mL or 250 L.1 mark
A small carton cannot hold hundreds of litres.
250 mL. - Match ruler, kitchen scales and measuring jug to length, mass and liquid amount.3 marks
Use the instrument designed for each quantity.
Ruler: length; scales: mass; jug: liquid amount. - A learner writes that a pencil has a mass of 15 cm. Explain and correct the unit type.2 marks
The quantity and unit must match.
A sensible possible pencil mass is 15 g; the actual pencil must be weighed.
Centimetres measure length, not mass. A mass could be stated in grams. - A parcel has a mass of 1000 g. Use to express its mass in kilograms.1 mark
The given equality states that 1000 grams is one kilogram.
1 kg
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics 2026
Length/mass/capacity/temperature; scaled instruments; partial/unmarked intervals; suitable units and accuracy.
Official curriculum source ↗