Perimeter of Polygons
The perimeter is the distance all the way around the outside of a shape. It's like walking around the edge of a playground or tracing your finger around the outside of a picture frame.
A polygon is a closed shape with straight sides. Squares, rectangles, and triangles are all polygons!
To find the perimeter of any polygon, we add up the lengths of all its sides.
Finding Perimeter
Here's how to find the perimeter of a polygon:
- Measure the length of each side
- Add all the side lengths together
- The sum is the perimeter!
Perimeter is measured in units of length like:
- inches (in)
- feet (ft)
- centimeters (cm)
- meters (m)
Special Shapes
Square: A square has 4 equal sides. To find its perimeter, multiply the side length by 4.
Perimeter of a square = Side + Side + Side + Side = 4 × Side
Rectangle: A rectangle has 2 pairs of equal sides. To find its perimeter, add all four sides.
Perimeter of a rectangle = Length + Width + Length + Width = 2 × Length + 2 × Width
Triangle: A triangle has 3 sides. To find its perimeter, add all three sides.
Perimeter of a triangle = Side 1 + Side 2 + Side 3
Try It: Interactive Perimeter Practice
Choose a shape, enter the side lengths, and check your answer.
Why Perimeter Matters
Knowing how to find perimeter helps us in many ways:
- Figuring out how much fence we need for a garden
- Finding how much ribbon we need to go around a gift box
- Measuring the distance around a picture frame
- Calculating how far we walk if we go around a park