📏 Measuring Length
Length tells us how long or tall something is. We measure length in centimetres and metres!
📏 Centimetres (cm)
A centimetre (cm) is a small unit of length. We use centimetres to measure short lengths — like a pencil or a book.
A ruler shows centimetres:
Always start measuring from the 0 mark — not the edge of the ruler!
✏️
Pencil
about 15 cm
📚
Exercise book
about 30 cm
🖊️
Crayon
about 8 cm
📏 Metres (m)
A metre (m) is a larger unit of length. There are 100 centimetres in 1 metre. We use metres to measure longer distances — like a room or a hallway.
1 metre = 100 centimetres
🚪
Doorway height
about 2 m
🏫
Classroom length
about 8 m
🌳
Tall gum tree
about 20 m
🤔 Estimating and Comparing
An estimate is a careful guess before measuring. Compare using words: longer, shorter, taller, the same length.
Comparing two objects:
Rope A is longer. Rope B is shorter.
Worked Examples
Example 1: Reading a ruler
A leaf starts at 0 cm and ends at the 7 cm mark. How long is the leaf?
The leaf is 7 cm long. ✅
Example 2: Choosing the right unit
Would you measure the length of your classroom in cm or m?
Metres (m) — classrooms are much too long for centimetres! ✅
Example 3: Converting
How many centimetres is 3 metres?
3 × 100 = 300 cm. Three metres is 300 centimetres. ✅
Key Vocabulary
A small unit of length. 100 cm = 1 m.
A larger unit of length. 1 m = 100 cm.
A careful guess before measuring.
Words to compare two lengths.
Knowledge Check
Question 1: A pencil is measured and goes from 0 to 14 on a ruler. How long is the pencil?
Question 2: How many centimetres are in 1 metre?
Question 3: Which unit would you use to measure the length of your shoe?
Question 4: Stick A is 22 cm. Stick B is 17 cm. Which stick is longer?
Question 5: A hallway is 5 metres long. How many centimetres is that?
Pax Says:
"Find a ruler and measure three objects at home! Write down the lengths in centimetres. Can you find something that is exactly 10 cm?"
Key Concepts Summary
- ✓ Centimetres (cm) are used for short lengths; metres (m) for long lengths.
- ✓ 1 metre = 100 centimetres.
- ✓ Always measure from the 0 mark on a ruler.
- ✓ An estimate is a careful guess before measuring.