of a circle is
I want to calculate

A circle has radius = 9

##### Calculate circumference (C):

C = 2πr

C = 2π * 9

C = 18π or 56.5487

d = 2r

d = 2 * 9

d = 18

##### Calculate Area (A):

A = πr2

A = π * 92

A = 81π or 254.469

C = 18π or 56.5487
d = 18
A = 81π or 254.469

C = 18π or 56.5487
d = 18
A = 81π or 254.469
##### How does the Circles Calculator work?
Free Circles Calculator - Calculates and solves for Radius, Diameter, Circumference, and Area of a Circle.
This calculator has 1 input.

### What 3 formulas are used for the Circles Calculator?

d=2r
A = 2πr2
C=2πr

For more math formulas, check out our Formula Dossier

### What 7 concepts are covered in the Circles Calculator?

area
Number of square units covering the shape
circle
the set of all points in the plane that are a fixed distance from a fixed point
circles
circumference
the perimeter of a circle or ellips
diameter
distance from two endpoints of a circle through the center
d = 2r
origin
On a two digit coordinate plane, the point (0, 0), where the x-axis and y-axis cross.
Distance from the center of a circle to the edge
C/2π