The circle is defined as the set of all points in a plane which having the same distance from a fixed point. Here the fixed point is known as the center of a circle and the distance between any point of the circle and the center of the circle is called the circle radius.

Circle
 The circle calculator is an online tool which will help us to calculate the diameter, area and circumference of any circle with known value of radius.
The circle diameter is defined as distance across the circle through the center points.

Diameter of a circle = $2r$
Where $r$ - radius of the circle.

Area of the circle is the space covered by the circumference on the plane surface.

Area of a circle = $\pi r^{}2$ sq. units
 
Where $r$ - radius of the circle = $\frac{diameter}{2}$  units

The circumference is defined as the distance around the circle.

Circumference of a circle = $2 \pi r$ 

Where $r$ - radius of the circle.