Finding the Area of a Circle How to find the area of a circle: The area of a circle can be found by multiplying pi (π = 3.14) by the square of the radius If a circle has a radius of 4, its area is 3.14*4*4=50.24 If you know the diameter, the radius is 1/2 as large.Finding the Area of a Circle. How to find the area of a circle:1  The area of a circle can be found by multiplying pi (π = 3.14) by the square of the radius. 2  If a circle has a radius of 4, its area is 3.14*4*4=50.24. 3  If you know the diameter, the radius is 1/2 as large.inding the Area of a Circle How to find the area of a circle: The area of a circle can be found by multiplying pi (π = 3.14) by the square of the radius If a circle has a radius of 4, its area is 3.14*4*4=50.24 If you know the diameter, the radius is 1/2 as large. Return to Top.