What is the perimeter?

The perimeter is the total distance around the outside of a shape or object. It is calculated by adding together the lengths of all the sides of the shape. The perimeter is often used to determine the amount of material needed to enclose a space, such as the fencing needed for a garden or the measurements needed for a floorplan. The formula to calculate the perimeter of a rectangle or square is P = 2(l + w), where P is the perimeter, l is the length, and w is the width. For a triangle, the perimeter is found by adding together the lengths of all three sides. The perimeter is measured in units such as meters, feet, or inches.