📐 Area & Perimeter
What You'll Learn
- The difference between area and perimeter
- How to calculate area using multiplication (length × width)
- How to calculate perimeter by adding all sides
Two Ways to Measure a Shape
When measuring a rectangle, there are two different questions you can ask:
- Perimeter — how far around the outside? (like fencing a yard)
- Area — how much space is inside? (like carpet for a floor)
Perimeter = the path around the shape (measured in units).
Area = the space inside the shape (measured in square units).
Calculating Area and Perimeter
For a rectangle with length L and width W:
- Area = L × W → a rectangle 5 units wide and 3 units tall has area = 5 × 3 = 15 square units
- Perimeter = 2 × (L + W) → same rectangle: P = 2 × (5 + 3) = 2 × 8 = 16 units
Builders use area to know how much flooring to buy. They use perimeter to know how much baseboard trim to install. Both measurements come from the same room but answer completely different questions!
Use the interactive tool below. Change the width and height and watch area and perimeter update instantly!
Course Complete!
You finished OKSTEM 3rd Grade Math! You covered place value, addition, subtraction, multiplication, division, fractions, and geometry. These are the building blocks for all of math going forward.
Explore More Courses →1. A rectangle is 6 units wide and 4 units tall. What is its area?
2. Same rectangle: 6 wide, 4 tall. What is its perimeter?
3. You want to put a fence around a garden. Do you need area or perimeter?