What is perimeter?
Perimeter is the distance around the edge of a two-dimensional shape. You measure the perimeter of a shape by adding the length of each of its sides. If you walk the distance around the edge of a playground, you are walking its perimeter. When measuring perimeter, it’s important all sides are measured using the same units. Common units for perimeter include centimeters, inches, and feet.
Measuring the perimeter of a square is easy since the length of each side is the same. If measuring a square-shaped rug with each side being 5 feet long, you would calculate the perimeter by adding 5 together four times. (5 + 5 + 5 + 5 = 20). This calculation would give you a perimeter of 20 feet.
When measuring the distance around a circle, the perimeter is called the circumference. One way to measure the perimeter of a circle is by wrapping string around the edge of the shape. Afterward, straighten the string and use a ruler or measuring tape to calculate its length. Calculating a circumference mathematically, requires the formula PI × d, where d is the diameter of the circle.
Why is perimeter important to learn?
Measuring perimeter helps students learn to quantify physical space and has many real-world applications. It’s important for students to see how these concepts are helpful in everyday living. Farmers use perimeter to measure the distance around the area where they want to plant crops. If putting up a fence, you need to know the distance around your yard before buying the materials.
For a fun, hands-on activity, ask students to trace around and measure the perimeter of several objects in your classroom. When finished, ask students for feedback regarding the shape of the objects they measured along with their method for finding the perimeter.