Area of a rectangle
A rectangle 6 cm by 4 cm has area 24 square centimetres.
Area is length multiplied by width.
Year 5
Calculate and compare the area of rectangles, and estimate the area of irregular shapes
Calculate the area of rectangles and estimate the area of irregular shapes using square units.
Lesson overview
Measurement
Area measures the amount of surface inside a shape. For rectangles, we can multiply the length by the width. For irregular shapes, we can estimate by counting full and part squares.
Compare areas
A 5 by 3 rectangle has less area than a 6 by 4 rectangle.
Compare the total number of square units.
Estimate irregular area
Count full squares first, then combine the part squares into whole ones.
estimate
An estimate is sensible, not exact.
Worked example
Find the area of a rectangle 8 cm by 7 cm.
- Use length times width.
- Multiply 8 by 7.
- 8 x 7 = 56.
- The area is 56 square centimetres.
Round 1: Learn it
Use multiplication for rectangles and square counting for estimates.
Finish this round to unlock Round 2: Show you know it.
Question 1
What is the area of a 6 cm by 4 cm rectangle?
Question 2
Which rectangle has greater area?
Question 3
Find the area of a rectangle 8 cm by 7 cm.
Question 4
What should you count when estimating the area of an irregular shape on a square grid?
use full and part squares
perimeter
Question 5
Which calculation gives the area of a 9 cm by 3 cm rectangle?
Common mistakes
Watch for these as you work through the lesson.
- Mixing up area and perimeter.
- Adding the sides instead of multiplying the dimensions.
- Ignoring part squares when estimating irregular area.
Related topics
These ideas connect closely to this lesson.
- Measure and calculate the perimeter of composite rectilinear shapes in centimetres and metres.
- Estimate volume and capacity and use all four operations to solve problems involving measure.