Measuring Perimeters
Measure the perimeter of simple 2-D shapes
What a learner can do afterwards
- Measure each side of a rectangle and add the lengths to find the perimeter
- Calculate the perimeter of a regular shape given the side length
- Explain that perimeter is the total distance around a shape
1 · Read
The perimeter of a shape is the total distance all the way around its outside edge. Imagine walking along every side of a shape, from your starting corner back to the same spot. The distance you walk is the perimeter.
Leo measures a small garden bed. Two sides are 6 m long and two sides are 4 m long. He adds 6 + 4 + 6 + 4 and gets 20 m. That is the perimeter of his garden bed.
If a shape is regular, all its sides are the same length. To find its perimeter fast, multiply the side length by the number of sides. A square with 4 cm sides has a perimeter of 4 x 4 = 16 cm.
Perimeter is the distance all the way around a shape: add up every side to find it.
More to read
9 Ways to Find Perimeter
Perimeter is the length all the way around the edge of a shape. Think about a fence around your yard. If you walked along the whole fence and added up every step, that total is the perimeter.
To find the perimeter of any shape, add up the length of every side. It does not matter if the shape is a triangle, a rectangle, or has five or six sides.
For shapes like squares and rectangles, there are quick tricks. A square has four equal sides, so you can multiply one side by 4. A rectangle has two pairs of equal sides, so you can add the length and width, then multiply by 2.
How to Find the Perimeter of a Shape
The perimeter of a shape is the total distance around its outside edge. Picture tracing your finger along every side of a shape without lifting it. When you get back to where you started, you have gone all the way around the perimeter.
To find the perimeter, measure the length of each side. Then add all those lengths together. This works for any closed shape, whether it is a triangle, a square, or an odd shape with many sides.
Some shapes have a shortcut. A rectangle has two long sides and two short sides that match. You can add the length and the width, then double that number to get the perimeter fast.
How to Find Area and Perimeter of a Shape
The perimeter is the length of the entire edge around a shape. It is different from area, which measures the space inside a shape.
To find the perimeter, figure out the shape you are measuring first. Then measure or write down the length of every side. Add all the side lengths together, and that sum is the perimeter.
For a rectangle, you only need the length and the width. Add them together, then multiply by 2, because a rectangle has two sides of each length.
How to Find the Area of Regular Polygons
A regular polygon is a shape where every side is the same length and every angle is the same size, like a square or a regular pentagon.
To find the perimeter of a regular polygon, you do not need to add up every side one by one. Since all the sides are equal, you can multiply the length of one side by how many sides the shape has.
For example, a regular hexagon has 6 equal sides. If each side is 4 cm long, the perimeter is 4 cm times 6, which equals 24 cm.
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