How to Calculate the Perimeter of a Shape
The perimeter of shapes is the summation of the length of each side of a shape. Perimeter for a circle is different: when a diameter equals one, then the perimeter equals pi. Contractors use perimeter for things such as to determine lengths of fences or putting a border around a room.
Other People Are Reading
Instructions
-
Non-Circular Shapes
-
1
Measure the length of each side of a shape. For example, a parallelogram may have sides of 3 inches, 3 inches, 5 inches and 5 inches.
-
2
Add the sides together. In the example, 3 plus 3 plus 5 plus 5 equals a perimeter of 16 inches.
-
-
3
Recalculate the perimeter to check your work. Since perimeter calculations involve adding three or more sides, each additional side adds to the chance of making a calculation error.
Circle
-
4
Measure the diameter of the circle. The diameter is the length from one end of a circle to the opposite end of the circle. For example, a circle may have a diameter of 10 inches.
-
5
Divide the diameter into two to determine the radius. In the example, the radius of the circle is 5 inches.
-
6
Multiply 2 by the radium and pi. In the example, 2 times 5 times 3.14, which equals a perimeter of 31.4 inches.
-
7
Recalculate the perimeter to check your work and eliminate the chances of a mathematical error.
-
1
References
- Photo Credit coloured shapes image by Leslie Batchelder from Fotolia.com
