Primary 3 · Measurement & Geometry

P3 area and perimeter

In P3, your child meets two ways to measure a flat shape. The perimeter is the distance around it, and the area is the space inside it. They find the perimeter of a rectangle, a square or an L-shape, and the area of a rectangle or a square in square units.

Taught in: Term 4
Syllabus: 3 skills
Usual slip: Adds the sides

Updated 11 October 2026

A 4 cm by 3 cm rectangle, its edge traced and its inside covered by squares

What your child learns in P3 area and perimeter

Three skills, each with what it looks like on a worksheet.

Follows the latest (2026) MOE syllabus

See the syllabus wording

concepts of area and perimeter of a plane figure
measuring area in square units, cm² and m², excluding conversion between cm² and m²
perimeter of rectilinear figure, rectangle, square
area of rectangle/square

Two different measures

Perimeter is the distance all the way around a shape, measured in cm or m. Area is the space inside it, measured in square units such as cm². One rectangle has both, and they are measured in different units.

Perimeter: around the edge

Area: the squares inside

Perimeter of any straight-sided shape

Add every side, all the way round. A rectangle has two lengths and two breadths. A square has four equal sides. An L-shape on a grid is traced edge by edge, so no side is missed.

Square: 4 × 5 cm

L-shape: count every edge

Area in square units

Area counts squares. Each square on a 1 cm grid is 1 cm², and a 1 m square is 1 m². Length × breadth counts a rectangle's squares in one step, and side × side a square's.

5 × 2 = 10 squares, so 10 cm²

Key facts and formulas

Term 4

PerimeterPerimeter is the distance all the way around. Add all the sides. $5 + 2 + 3 + 3 + 2 + 5 =$ $20\,\text{cm}$
Perimeter of a rectangle $\text{2 lengths} + \text{2 breadths}$ Example $7 + 4 + 7 + 4 =$ $22\,\text{cm}$
Perimeter of a square $4 \times \text{side}$ Example $4 \times 6 =$ $24\,\text{cm}$
AreaArea is the space inside. Count the squares: each small square is 1 cm².
Area of a rectangle $\text{length} \times \text{breadth}$ Example $7 \times 4 =$ $28\,\text{cm}^{2}$
Area of a square $\text{side} \times \text{side}$ Example $6 \times 6 =$ $36\,\text{cm}^{2}$

Words to know

Perimeter: The distance all the way around a shape. It is a length, in cm or m.
Area: The space inside a shape, found by covering it with squares.
Square centimetre (cm²): The area of a square with sides of 1 cm. Area is always in square units.
Length and breadth: The two sides of a rectangle. Breadth is the word schools use for the shorter side.

The sentence that costs the mark

A rectangle has sides of 5 cm and 3 cm. What is its area?

What the working usually does

addthe sides=16 cm

Adds all four sides. That gives 16, but 16 cm is the perimeter, the distance around, not the area.

What the question asked

multiplythe sides=15 cm²

Multiplies the length by the breadth to cover the inside. Area is counted in squares, so the unit is cm².

Both use the same two numbers and both give a real answer, so nothing looks careless. The unit gives it away: a distance around is in cm, a space inside is in cm². Ask "the edge or the inside?" before picking a method.

The same P3 area and perimeter question, worked properly

Lah works through it the way she does every question in StudyLah: one step at a time, marking the picture as she goes.

A rectangular card measures 7 cm by 6 cm, as shown. What is its area?

Step 1 of 4▌

The card is 7 cm long and 6 cm broad. We want its area, the space inside it.
Adding all four sides gives 7 + 6 + 7 + 6 = 26 cm. That is the perimeter, the distance around the edge.
The area is length × breadth, so 7 × 6 = 42 cm². Area counts squares, so the unit is cm².
So the area of the card is 42 cm².

Every question in StudyLah comes with a walkthrough like this one.

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Three quick P3 area and perimeter questions

Try them together, then tap to check.

Question 1

The shaded figure below is drawn on a grid of 1-cm squares. Find its perimeter.

Show answer

Answer24 cm. Trace the edge all the way round and count each 1 cm side. The inside squares do not count.

Question 2

Find the area of the square drawn below.

Show answer

Answer49 cm². All four sides of a square are 7 cm, so the area is 7 × 7 = 49 cm².

Question 3

The figure below is made of 1-metre squares. What is the area of the shaded figure?

Show answer

Answer6 m². There are 5 whole squares and 2 half squares. Two halves make one whole, so 5 + 1 = 6.

Helping at home

How to tell it has clicked

Draw any rectangle and ask two things: how far is it around the edge, and how much space is inside? A child who adds for the first and multiplies for the second has it. One who does the same thing twice has not.

The quickest tell is the unit. An area answer in cm, not cm², means the perimeter method was used, whatever the number.

Try this tonight

Use a place mat or a floor tile. Run a finger around the edge: that is the perimeter, a length. Then press a flat palm on top: that is the area, a covering. Same shape, two questions.

When homework says "area", ask your child to say "space inside" before working. For "perimeter", "distance around". Naming the job first stops the swap.

Before and after P3 area and perimeter

Builds on
Primary 2 Length
Measures and compares lengths in m and cm
Builds on
Primary 3 Multiplication and Division
Multiplies and divides, and reads the remainder
You are here
Primary 3 Area and Perimeter
Measures around a shape and inside it
Leads to
Primary 4 Area and Perimeter
Splits for area, traces for perimeter
Leads to
Primary 4 Rectangles and Squares
Knows which sides and corners must match

More in Primary 3

Struggling with the working rather than the topic itself? How to help your child with problem sums

See how your child is doing on this topic

StudyLah marks each step separately, so you can see whether it was the setup or the arithmetic that cost the mark.

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