Area of Circle π (pi) Formula
This formula calculates the area of a circle in terms of the geometric constant (pi). This is the traditional form of the area of a circle formula, see the alternative formula in terms of the circle constant (tau).
Expression  Description 

The area of the circle.  
The geometric constant (pi), where  
The radius of the circle. 
The area of a circle is given by the constant (pi) multiplied by the radius of the circle squared. For example, to find the area of a circle with a radius of length 5 the formula is:
Substituting the value of into the formula, approximately , and evaluating the multiplication gives the area of the circle
The area of a circle with radius length is approximately units squared.
The area of the circle formula can be using calculus^{[1]} or using a visual proof^{[2]}.

Derive Area of Circle Formula Example

Area of Circle Visual Proof Example