Year 5 · Mathematics · Measurement
Area and perimeter
Find the perimeter of shapes and the area of rectangles using multiplication, choosing sensible metric units such as square centimetres and square metres.
Awaiting educator review. This material was drafted by our content team with AI assistance and is waiting for review by a qualified educator. Please check it suits your child before using it. Created 10 October 2026.
Learning goals
Learners will
- Calculate the perimeter of rectangles and other straight-sided shapes.
- Calculate the area of a rectangle by multiplying its length by its width.
- Choose sensible units for area and perimeter.
Success looks like
- I can find the perimeter of a shape by adding the lengths of all its sides.
- I can find the area of a rectangle using length × width.
- I can explain the difference between area and perimeter.
- I can choose square centimetres or square metres to measure an area.
The big idea
Perimeter is the distance all the way around a shape. Imagine walking around the edge of a paddock: the total distance you walk is the perimeter. To find it, add the lengths of every side. Perimeter is measured in units of length such as centimetres (cm) and metres (m).
Area is how much surface a shape covers. Imagine laying carpet tiles over a floor: the number of square tiles you need is the area. Area is measured in square units such as square centimetres (cm²) and square metres (m²).
A rectangle that is 4 cm long and 3 cm wide can be covered by 3 rows of 4 one-centimetre squares. That is 3 × 4 = 12 squares, so the area is 12 cm². Instead of counting squares, we can use the rule: area of a rectangle = length × width.
For the perimeter of the same rectangle, add all four sides: 4 + 3 + 4 + 3 = 14 cm. A quick way is to add the length and width and double the result: (4 + 3) × 2 = 14 cm.
Choose units that suit the size of the shape. A book cover is sensibly measured in cm², while a backyard or a classroom floor is measured in m².
Shapes with the same area can have different perimeters. Twelve square tiles can make a 3 × 4 rectangle (perimeter 14 units) or a 1 × 12 rectangle (perimeter 26 units). Area and perimeter measure different things.
Worked examples
Area and perimeter of a rectangle
A vegetable garden is a rectangle 8 m long and 5 m wide. Find its perimeter and area.
- Perimeter: add all four sides: 8 + 5 + 8 + 5 = 26 m.
- Area: length × width = 8 × 5 = 40.
- Area is measured in square units, so the area is 40 m².
Answer: Perimeter = 26 m, area = 40 m².
A square
A square sandpit has sides 3 m long. Find its perimeter and area.
- A square has four equal sides, so the perimeter is 4 × 3 = 12 m.
- Area = length × width = 3 × 3 = 9 m².
Answer: Perimeter = 12 m, area = 9 m².
Same area, different perimeters
Find every rectangle with whole-number sides and an area of 12 cm², and compare their perimeters.
- Find pairs of whole numbers that multiply to 12: 1 × 12, 2 × 6 and 3 × 4.
- 1 cm by 12 cm: perimeter = (1 + 12) × 2 = 26 cm.
- 2 cm by 6 cm: perimeter = (2 + 6) × 2 = 16 cm.
- 3 cm by 4 cm: perimeter = (3 + 4) × 2 = 14 cm.
Answer: All three rectangles have an area of 12 cm², but their perimeters are 26 cm, 16 cm and 14 cm.
Practice check
Have a go, then check your answers. Each answer comes with an explanation.
Answer guide for parents
What is the area of a rectangle that is 7 cm long and 4 cm wide?
28 cm² — Area = length × width = 7 × 4 = 28, measured in square centimetres: 28 cm².
What is the perimeter of a rectangle that is 10 m long and 3 m wide?
26 m — 10 + 3 + 10 + 3 = 26 m.
Which unit is the most sensible for measuring the area of a lounge room floor?
Square metres — Area needs square units, and a room is large, so square metres are the most sensible.
A square has a perimeter of 20 cm. How long is each side?
5 cm — A square has 4 equal sides, so each side is 20 ÷ 4 = 5 cm.
What is the area, in square centimetres, of a square with sides 9 cm long?
81 cm² — Area = 9 × 9 = 81 cm².
A rectangular paddock is 25 m long and 15 m wide. How many metres of fencing are needed to go all the way around it?
80 m — Perimeter = (25 + 15) × 2 = 40 × 2 = 80 m.
A rectangle has an area of 24 m². One side is 6 m long. How many metres long is the other side?
4 m — Length × width = 24, and 6 × 4 = 24, so the other side is 4 m.
A bedroom floor is a rectangle 4 m long and 3 m wide. Carpet costs $30 per square metre. How many dollars will it cost to carpet the floor?
$360 — Area = 4 × 3 = 12 m². Cost = 12 × $30 = $360.
Watch out for
- Mixing up area and perimeter. Link perimeter to a fence (around the edge) and area to carpet (covering the inside).
- Writing area in plain units such as cm instead of cm². Remind the learner that area counts squares.
- Adding only two sides to find the perimeter of a rectangle. Ask the learner to trace around the whole shape with a finger and count the sides.
Tips for parents
- Measure real things together: a table top, a rug or a garden bed. Real measurements make the ideas stick.
- Make a 1 m × 1 m square from newspaper so the learner can see how big a square metre really is.
- Ask “Is this an area question or a perimeter question?” before any calculation.
Go further
- Design a backyard on grid paper with a lawn, a veggie patch and a pool. Work out the area and perimeter of each part.
- With 24 m of fencing, what rectangular dog run has the biggest area? Test different lengths and widths with whole numbers.
- Measure the floor of each room in your home in metres, round to the nearest metre, and estimate the total floor area.