Perimeter Calculator
Calculate the perimeter (or circumference) of common shapes. Select a shape, enter the dimensions, and get the perimeter and area instantly.
The perimeter is the total distance around the outside of a two-dimensional shape. For simple shapes, the perimeter formulas are straightforward: rectangles use P = 2(l + w), triangles use P = a + b + c, circles use C = 2πr (circumference), and regular polygons use P = n × s where n is the number of sides and s is the side length.
Perimeter calculations are essential in everyday applications like fencing a yard, framing a picture, measuring running tracks, and cutting fabric or ribbon. For construction, knowing the perimeter helps determine the amount of baseboard, fencing, or edging material needed.
This calculator also computes the area as a bonus output. For triangles with all three sides known, it uses Heron's formula: A = √(s(s-a)(s-b)(s-c)) where s is the semi-perimeter (a+b+c)/2. Understanding the relationship between perimeter and area is important. Shapes with the same perimeter can have very different areas, and among all shapes with a given perimeter, the circle encloses the maximum area.