(Jump to Area of a Rectangle or Perimeter of a Rectangle)

A rectangle is a four-sided flat shape where every angle is a right angle (90°).


quadrilateral right key means "right angle"

quadrilateral equal key are equal sides

quadrilateral equal key2are equal sides
right arrowEach internal angle is 90°
right arrow

Opposite sides are parallel and of equal length (so it is a Parallelogram).

Play with a rectangle:

Area of a Rectangle

rectangle area 

Area = a × b

Example: A rectangle is 6 m wide and 3 m high, what is its Area?

Area= 6 m × 3 m
= 18 m2

Perimeter of a Rectangle

The Perimeter is the distance around the edges.

rectangle perimeter 

The Perimeter is 2 times (a + b):

Perimeter = 2(a+b)

Example: A rectangle is 12 cm long and 5 cm tall, what is its Perimeter?

Perimeter = 2 × (12 cm + 5 cm)
= 2 × 17 cm
= 34 cm

Diagonals of a Rectangle

rectangle diagonals 

A rectangle has two diagonals, they are equal in length and intersect in the middle.

rectangle diagonal calculation 

A diagonal's length is the square root of (a squared + b squared):

Diagonal "d" = √(a2 + b2)

Example: A rectangle is 12 cm wide, and 5 cm tall, what is the length of a diagonal?

rectangle diagonal example

d = √(122 + 52)
= √(144 + 25)
= √169
= 13 cm

Golden rectangle

Golden Rectangle

There is also a special rectangle called the Golden Rectangle: