Perimeter Calculator

Calculate the perimeter of various 2D shapes quickly and accurately. Select a shape, enter the dimensions, and get instant results with the formulas used.

Select Shape

Side Length

Length

Width

Radius (or enter Diameter below)

Diameter (optional if radius provided)

Side 1

Side 2

Side 3

Side Length

Number of Sides

Side Length

How to Use the Perimeter Calculator

Select the shape you want to calculate the perimeter for from the dropdown menu
Enter the required dimensions for your selected shape
Click the "Calculate Perimeter" button
View your result along with the formula used for the calculation

Supported Shapes

Square: A quadrilateral with all sides equal
Rectangle: A quadrilateral with opposite sides equal
Circle: Calculate circumference (circle's perimeter)
Triangle: Any triangle with three sides (all types supported)
Regular Polygons: Pentagon, hexagon, and custom polygons

What is Perimeter?

Perimeter is the total distance around the outside of a two-dimensional shape. It is calculated by adding up the lengths of all the sides of the shape. For circles, the perimeter is called the circumference and is calculated using the formula 2πr, where r is the radius.

Common Formulas

Square: P = 4 × side
Rectangle: P = 2 × (length + width)
Circle: C = 2πr or C = πd (where r = radius, d = diameter)
Triangle: P = side A + side B + side C
Regular Polygon: P = number of sides × side length