Every rectangle has an area and a perimeter. They answer different questions.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
Area is inside
Carpet for a floor, paint for a wall, grass for a lawn. All area.
Perimeter is around
Fence for a garden, ribbon round a box, edging for a path. All perimeter.
The common mistake
Multiplying all the sides to find area is wrong. Area is only width times height.
Two different questions
Area asks how much surface is inside. Perimeter asks how long the boundary is. Painting a wall is an area problem; putting a fence round a garden is a perimeter problem. Deciding which question the situation is asking is the whole skill.
The units tell you which is which
Area comes in square units — square centimetres, square metres. Perimeter comes in plain length units. If your answer to a perimeter question has "square" in the unit, you calculated the wrong thing. The units are a built-in check.
One does not decide the other
A 1 by 12 rectangle and a 3 by 4 rectangle both have area 12, but their perimeters are 26 and 14. Two shapes can share an area and differ wildly in perimeter, or share a perimeter and differ in area. They measure genuinely different things.
Step 2: Try It Yourself
Both numbers, for the same rectangle. Watch how differently they change.
Area · squares inside
24
Perimeter · walk around
20
6 × 4 = 24 · 6 + 4 + 6 + 4 = 20
Area counts the squares inside. Perimeter measures the walk all the way round.
Step 3: Watch an Example
One step at a time.
Watch Leo Choose
Leo needs to buy a fence for a garden 8 m by 5 m.
- Step 1
He asks whether the fence goes inside or around.
Step 4: Your Turn
Practice makes it stick.
The Carpet
Problem 1 of 3
A room is 7 m by 4 m. How much carpet covers the floor?
square metres
The Ribbon
Problem 2 of 3
A box top is 7 cm by 4 cm. How much ribbon goes round the edge?
cm
Same Perimeter
Problem 3 of 3
A 6 by 2 rectangle and a 5 by 3 rectangle both have perimeter 16. What is the area of the 5 by 3?
square units
Which One Is It?
1 of 4
Paint for a wall. Area or perimeter?
2 of 4
Edging round a flower bed. Area or perimeter?
3 of 4
A rectangle 8 by 3. What is its area?
4 of 4
A rectangle 8 by 3. What is its perimeter?
Step 5: Quick Check
Show what you know.
Question 1 of 2
A rectangle 9 by 4. What is its area?
Question 2 of 2
A rectangle 9 by 4. What is its perimeter?
What You Learned
- Area is the space inside. Perimeter is the distance around.
- Area uses square units. Perimeter uses plain units.
- Two rectangles can share a perimeter and have different areas.