Circle Calculator
Don't remember the formulas for the other two parts of a circle (radius, diameter, circumference, or area) when you only know one? To the rescue is Circle Calculator. Enter the circle radius, diameter, circumference, or area and it will solve for the other three!
Circle Definition
A circle is a closed two-dimensional figure in which the set of all the points in the plane is equidistant from a given point called “centre”. Every line that passes through the circle forms the line of reflection symmetry. Also, it has rotational symmetry around the centre for every angle.

Definitions Related to Circle
Arc: A curved line that is part of the circumference of a circle.
Circumference: The distance around the circle.
Diameter: The longest distance from one end of a circle to the other.
Origin: The center of the circle
pi (π): A number, 3.14159, equal to (the circumference) / (the diameter) of any circle.
Radius: Distance from center of circle to any point on it.
Circle Formulas
- D = 2R
- C = 2πR
- A = πR2
Where:
R is Radius of a circle
D is Diameter of a circle
C is Circumference of a circle
A is Area of a circle
π is 3.14159