Select the shape of which you want to calculate the circumference:
Circumference calculator
Calculate the circumference of a shape
Calculate the perimeter of various geometric shapes
Circle
The perimeter of a circle can be calculated using the formula:
2πr
where r is the radius of the circle and π is a mathematical constant (approximately equal to 3.14159).
Square
A square is a shape with four equal sides. The perimeter of a square is simply four times the length of one of its sides, or:
4*s
where s is the length of a side.
Rectangle
A rectangle has four sides, but unlike a square, the opposite sides are equal to each other. Therefore, the perimeter of a rectangle is calculated as:
(2*l) + (2*b) or 2*(l+b)
where l is the length and b is the width.
Triangle
The perimeter of a triangle is the sum of the lengths of its three sides. In the case of an equilateral triangle, where all sides are equal, the perimeter is simply three times the length of a side.
Polygons
Polygons are shapes with more than 4 angles. Below are a few examples of polygons, the pentagon and the hexagon:
For regular polygons (shapes with equal sides and angles), such as a pentagon or a hexagon, the perimeter is the product of the number of sides and the length of a side.
When calculating the perimeter of these shapes, it's important to be consistent with the units of measurement used. The result will be in the same unit as that used for the dimensions of the shape. For example, if the radius of a circle is measured in centimeters, the perimeter will also be in centimeters.