Perimeter Formulas

As you can see, perimeters can have many applications. Let’s take a look at the general formula for a perimeter.

	Notation	Formula
Perimeter		Add up the length of all sides

Perimeter of Rectangle

In order to find the perimeter of a rectangle, you should understand what a rectangle is. Even when rectangles are different sizes, they all share the same properties. The table below has these properties as well as how to find the perimeter of any rectangle.

Property 1	A polygon with four sides
Property 2	Opposite sides are parallel and congruent
Property 3	Has four right angles
Perimeter

The length and width of a rectangle correspond to the longest side and the shortest side.

Perimeter of Square

In order to find the perimeter of a square, you should understand what a square is. Even when squares are different sizes, they all share the same properties. The table below has these properties as well as how to find the perimeter of any square.

Property 1	A polygon with four sides
Property 2	Opposite sides are parallel, congruent and are all the same size
Property 3	Has four right angles
Perimeter

Because of property 2, where all sides of a square are the same size, you can simply add the sides 4 times, which is the same as multiplying one side four times.

Perimeter of Circle

In order to find the perimeter of a circle, you should understand what a circle is. Even when circles are different sizes, they all share the same properties. The table below has these properties as well as how to find the perimeter of any circle.

Property 1	A set of points, or a line, that is shaped in an O
Property 2	All points, or points on the line, are equidistant from the centre
Radius	The distance from the centre point to the outside of the circle
Diameter	The distance from one end to another end of the circle through the centre
Perimeter	Called the circumference
Circumference

Perimeter of Equilateral Triangle

In order to find the perimeter of an equilateral triangle, you should understand what an equilateral triangle is. Even when equilateral triangles are different sizes, they all share the same properties. The table below has these properties as well as how to find the perimeter of any equilateral triangle.

Property 1	A triangle, which has three lines and three interior angles
Property 2	All three angles are the same size, 60 degrees
Property 3	All sides are the same length
Perimeter

Because of property 3, we can multiply the three sides of the same length by 3 to get the perimeter.

Perimeter of Isosceles Triangle

In order to find the perimeter of an isosceles triangle, you should understand what an isosceles triangle is. Even when isosceles triangles are different sizes, they all share the same properties. The table below has these properties as well as how to find the perimeter of any isosceles triangle.

Property 1	A triangle, which has three lines and three interior angles
Property 2	Has two angles that are same size
Property 3	Has two sides are the same length
Perimeter

Because of property 3, we can multiply the 2 sides of the same length by 2 and add the length of the base(b) to get the perimeter.

Perimeter of Scalene Triangle

In order to find the perimeter of a scalene triangle, you should understand what a scalene triangle is. Even when scalene triangles are different sizes, they all share the same properties. The table below has these properties as well as how to find the perimeter of any scalene triangle.

Property 1	A triangle, which has three lines and three interior angles
Property 2	All three angles are a different size
Property 3	All three sides are a different size
Perimeter

Because of property 3, you need to add all sides to get the perimeter.

Perimeter of Rhombus

In order to find the perimeter of a rhombus, you should understand what a rhombus is. The table below has these properties as well as how to find the perimeter of any rhombus.

Property 1	A shape with four sides
Property 2	Opposite sides are parallel
Property 3	All four sides are congruent
Perimeter