Perimeter

The perimeter of a polygon (or any other closed curve, such as a circle) is the distance around the outside.

Here are some formulas for the perimeters of common plane figures.

Perimeter Formulas
Shape	Formula	Variables
Square	P = 4s	s is the length of the side of the square.
Rectangle	P = 2L + 2W	L and W are the lengths of the rectangle's sides (length and width).
Triangle	a + b + c	a, b, and c are the side lengths.
Right Triangle, with legs a and b (see Pythagorean Theorem)		a and b are the lengths of the two legs of the triangle
Circle	P = C = 2πr = πd	r is the radius and d is the diameter.