Primary 2 maths · Measurement & time · About 8 minutes
Choose suitable measurement units
Decide what you are measuring before choosing a unit.
Start the interactive lesson →Practise: Measure match
What you will learn
- Choose suitable measurement units
Models used: number sentences, stories, diagrams.
Before you start
Choose a unit that fits what you measure
Would you measure the length of a pencil in centimetres, kilograms or litres?
First decide what you are measuring. A pencil’s length is a distance, so use a length unit.
Length → centimetres or metres
A pencil measured in centimetres Choose a mass unit. Read each value with the heading above its column.
Mass tells us how heavy something is. Use grams for a light object and kilograms for a heavier one.
Choose a mass unit What we measure Suitable unit Mass of an apple grams Mass of a child kilograms Match the kind of measurement first. Read each value with the heading above its column.
Liquid volume tells us how much liquid a container holds. Litres suit a bottle or jug.
Match the kind of measurement first What we measure Suitable unit Liquid in a jug litres Length of a classroom metres Length of a pencil centimetres Our pencil question asks for length, so centimetres fit. Kilograms measure mass and litres measure liquid volume.
Pencil length: 12 cm
Centimetres answer a length question
What did the picture help us see?
Our pencil question asks for length, so centimetres fit. Kilograms measure mass and litres measure liquid volume.
Worked example: A new example, together
Choose a suitable unit for the liquid in a bucket.
Decide what you are measuring before choosing a unit.
Comparing measurements requires matching the amount and unit.
🪣A bucket: how much liquid can it hold? Identify the kind of quantity.
🪣A bucket: how much liquid can it hold? Choose a suitable unit for the liquid in a bucket.
litres
The liquid in a bucket is suitably measured in litres.
🪣A bucket: how much liquid can it hold? Units must match the amount, not just the size of the number.
🪣A bucket: how much liquid can it hold? Check the result against the question we started with.
Re-read the labels and unit before comparing the numbers.
We found litres. Comparing measurements requires matching the amount and unit.
🪣A bucket: how much liquid can it hold?
Common mistakes to discuss
- Choosing by the size of the number. Choose the unit by the size of the object. A pencil is about 12 cm; 12 m would be longer than a classroom.
Check your understanding
- Choose suitable measurement units
- choose a unit that fits the measurement
- check the answer against the original quantities and units
Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.
Try this lesson →Related Primary 2 lessons
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- Measure and compare mass in grams and kilogramsMeasure and compare mass in grams and kilograms · About 8 minutes