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Rectangle Area Calculator


Our rectangle area calculator finds the area, perimeter, and diagonal of a rectangle by considering its lengths and width. With the help of a maximum area of a rectangle calculator, you can find the area of the given coordinates of four corners of a rectangle as well. 

What Is a Rectangle?

A rectangle is a type of quadrilateral with four sides, four corners, and four angles that are equal to 90 degrees. 

In a rectangle, the alternate sides are equal and parallel to each other.

Area of a Rectangle Formula:

A rectangle is a four-sided polygon that has four angles of 90 degrees. By using the area of the rectangle calculator, you can find a rectangle's area, perimeter, and diagonal. The area of the rectangle formula is;

Area of a rectangle = L * W

Area of a rectangle = Length * Width 

You can calculate the area of a rectangle with the help of the rectangle area calculator. It uses the following units to represent the area of a rectangle.

  • mm^2
  • cm^2
  • dm^2
  • m^2
  • km^2
  • in^2
  • ft^2
  • yd^2
  • mi^2

How To Find The Area Of a Rectangle?

The best feature of our rectangular area calculator is that if you have an area and want to calculate its length or width you can do so. Suppose that a rectangle has a length of 4cm and a width of 6cm. What is the area of a rectangle?

rectangle picture
Given Data:

Length = 4cm
Width = 6cm

To Find:

Area = A =?

The formula for area of a rectangle:

A = l * w 

Put values in the formula to find an area of rectangle

A = 4cm * 6cm

A = 24 cm^2

We can also find the length or width by adjusting the rectangle area formula as follows:

L = A/W

L= 24/6

L = 4cm

Find The Perimeter of a Rectangle 

Here we find the perimeter of the same rectangle that we suppose in the example. The equation for perimeter is;

P = a + b + a + b

Which can be written as 

P = 2 (a + b)

P = 2 (4 + 6)

P = 10cm

Find The Diagonal Of a Rectangle:

Calculate the diagonal of a rectangle for the same rectangle that we suppose upper. The diagonal of a rectangle formula is as follows;

d^2 = a^2 + b^2

Take a square root on both sides we get: 

$$d = \sqrt{a^{2} + b^{2}}$$

a^2 = 16, b^2 = 24

a + b = 40

d = 40

d = 6.326cm

Working of Rectangle Area Calculator: 

Stay focused on the following points to understand the working of our area of shaded rectangle calculator.


  • The length of one side of the rectangle 
  • Put the width of the rectangular side 
  • Choose a unit in which you want to calculate area 
  • Tap “Calculate”


  • Area of rectangle
  • Perimeter of a rectangle 
  • Diagonals
  • Step-by-step calculations 

Properties Of a Rectangle:

There are several properties of a rectangle that are as follows:

  • A rectangle is a quadrilateral 
  • It's center is equidistance from its vertices so it is circumcircle
  • All corner angles are equal to each other
  • It is rectilinear which means that all sides meet at 90 angles 
  • Opposite sides of the rectangle are equal and parallel to each other 
  • The sum of all angles is equal to the 360 degrees 
  • Each diagonal of the rectangle bisects the other 
  • Both opposite-sided diagonals have the same length 


Is Square a Rectangle?

A square is always a rectangle and the rectangle is not always a square. The rectangle’s opposite sides are equal but parallel to each other. Their adjacent sides may or may not be equal. That's why always rectangles are not square. 

What Are The Golden Rectangles?

The rectangle whose side lengths are in a golden ratio. The formula to find the golden ratio of the rectangle is as follows:

(a + b) / a = a / b = ϕ

Where the value of ϕ is approximately 1.618.


From the source Wikipedia: Rectangle, Characterizations, Classification, Properties, Formulae, Theorems, Crossed rectangles, Other rectangles. 

From the source Khan Academy: Area of rectangles review, what is an area?