# Area of a Rectangle

LAST UPDATE: February 2nd, 2022

## Method #1 – Area from Length & Width

### Formula – How to calculate the area of a triangle using the Length & Width

Area = Length x Width

##### Example

A rectangle has a length of 10 and a width of 30

Area = 10 x 30 = 300

## Method #2 – Area from Perimeter

### Formula – How to calculate the area of a triangle using the perimeter

Step 1 – Find the length of the other side

Width = (Perimeter – Length – Length) ÷ 2

Step 2 – Find the area of the rectangle

Area = Length x Width

##### Example

A rectangle has a length of 10 and a perimeter of 60

Width = (60 – 10 – 10) ÷ 2 = 40 ÷ 2 = 20

Area = 10 x 20 = 200

## Method #3 – Area from Diagonal

### Formula – How to calculate the area of a rectangle using the diagonal

Step 1 – Find the width of the other side

Width = √(Diagonal2 – Length2)

Step 2 – Find the area of the rectangle

Area = Length x Width

##### Example

A rectangle has a length of 10 and a diagonal of 30

Width = √(302 – 102) = √(900 – 100) = √800 = 28.2842

Area = 10 x 28.2842 = 282.842