0 5 10 m

MEASURING LENGTH

Length is how long something is from one end to another.
We use standard units to measure length accurately! 📐
WHAT IS LENGTH?
  • Length tells us how long something is from one end to the other.
  • We can measure length using non-standard and standard units.
  • Standard units help us measure accurately and compare easily.
Measure carefully, get it just right!
UNITS OF LENGTH
Millimetre
(mm)
Very small lengths (e.g., pencil tip)
Centimetre
(cm)
Small lengths (e.g., eraser, notebook)
Metre
(m)
Standard unit for length (e.g., door)
Kilometre
(km)
Very large distances (e.g., roads)
10 mm = 1 cm ➔ 100 cm = 1 m ➔ 1000 m = 1 km
QUICK FACTS
  • We measure length in a straight line.
  • The standard unit for length is metre (m).
  • Smaller units are centimetre (cm) and millimetre (mm).
  • Bigger distance unit is kilometre (km).
  • Always align the start point exactly at 0 on a ruler.
  • Choose the right tool for accurate measurement.
Always compare units of the same kind!
NON-STANDARD UNITS

These are old methods and are not the same for everyone:

✋
Hand Span
🦶
Foot Print
💪
Cubit Arm
⚠️ Note: They are not accurate and change from person to person!
MEASURING TOOLS
📏
Ruler
Used to measure small lengths in cm and mm.
🎗️
Measuring Tape
Used by tailors & builders to measure longer lengths in m and cm.
☸️
Measuring Wheel
Used to measure very long distances on roads or fields.
HOW TO MEASURE LENGTH USING A RULER
1 Place the Object
Lay the object flat along the edge of the ruler.
2 Start at Zero (0)
Make sure one end of the object starts exactly at the 0 mark.
3 Read the Number
Look at the other end. The number it matches is the total length!
Interactive Measuring Practice: How long is this object?
0 1 2 3 4 5 6 7 8 9
Length of the Pencil = cm
CONVERSION EXAMPLES
1. Convert cm to mm: 5 cm = 5 × 10 = mm
2. Convert m to cm: 3 m = 3 × 100 = cm
3. Convert km to m: 2 km = 2 × 1000 = m
4. Complex Step: 150 cm = 1 m + cm
CONVERSION TABLE & SCALES
Smaller Unit
Larger Unit
Relation
10 millimetres (mm)
1 centimetre (cm)
10 mm = 1 cm
100 centimetres (cm)
1 metre (m)
100 cm = 1 m
1000 metres (m)
1 kilometre (km)
1000 m = 1 km
Compare Units (Select <, >, or =):
6 cm 14 cm
4 m 250 cm
1000 m 1 km
MEASURING LENGTH IN REAL LIFE
📘
Length of a Book
~ 25 cm
🪟
Height of a Window
~ 1.5 m
🏫
Length of a Classroom
~ 8 m
🛣️
Distance Between Cities
~ 150 km
THINK AND ANSWER
KEY POINTS TO REMEMBER
  • Length measures object sizing spans from end to end.
  • Standard Units globally approved: mm, cm, m, km.
  • Metric Scale ratios: 1 cm = 10 mm, 1 m = 100 cm, 1 km = 1000 m.
  • Always place the edge edge border alignment line safely on 0.
  • Pick relevant tool scales based on small, intermediate, or distant objects.
ACCURATE SCALE