# Area of Circle

The **area of a circle** is an area, which is bounded by a circular line. For example, a circular garden that has a fence around it. The area of the garden is like the **area of a circle** and the length of a fence is like a circumference of a circle.

To calculate the area of a circle, we need to know its radius or diameter and the pi number (Ludolph's number), its value is 3,141592... In a circle, the diameter is d = 2 × radius "r". The elementary unit of the area is one square metre, it means the second power of one metre (1 m^{2}).

d=2 × r, also r = d / 2

## Area of Circle - formula

**Area of Circle** = (Ludolph's number × diameter^{2})/4

or

**Area of Circle** = Ludolph's number × radius^{2}

A = (π × d^{2}) / 4 = π × r^{2}