Perimeter

Perimeter is the distance around a two-dimensional shape.

Example: the perimeter of this rectangle is 7+3+7+3 = 20

perimeter of rectangle

Example: the perimeter of this regular pentagon is 3+3+3+3+3 = 5×3 = 15

perimeter of pentagon

 

The perimeter of a circle is called the circumference:

Circumference = 2π × radius

  circle

Perimeter Formulas

Triangle   Triangle
Perimeter = a + b + c
Square   Square
Perimeter = 4 × a
a = length of side
Rectangle   Rectangle
Perimeter = 2 × (w + h)
w = width
h = height
Parallelogram   Quadrilateral
Perimeter = a + b + c + d
circle   Circle
Circumference = 2πr
r = radius
Sector   Sector
Perimeter = r(θ+2)
r = radius
θ = angle in radians
ellipse   Ellipse
Perimeter = very hard!