Units of Length – Grade 7
This lesson introduces the concept of length and the units used to measure it.
What This Lesson Covers
- The meaning of length
- Different measurements related to length
- The SI unit of length
- Common units used to measure length
3.2 Length
Length is the distance between two points. It is used to measure how long, tall, wide, or far an object is.
We use length measurements in everyday life, such as measuring the height of a person or the distance between two places.
Measurements Related to Length
- Length
- Width
- Breadth
- Height
- Depth
- Diameter
- Radius
- Circumference
These are all different ways of measuring distance or size.
3.2.1 Units of Length
The international standard unit (SI unit) of length is the metre (m).
Multiples and Sub-multiples of the Metre
- 100 centimetres (cm) = 1 metre (m)
- 10 decimetres (dm) = 1 metre (m)
- 10 metres = 1 decametre (Dm)
- 100 metres = 1 hectometre (Hm)
Important Note
When adding or comparing lengths, all measurements must first be converted to the same unit.
Interactive Activity: Which Unit Is Best?
Choose the most suitable unit of length for each example.