Circle Calculator
Enter any one property of a circle — radius, diameter, area, or circumference — and instantly calculate all the others.
Calculated Circle Properties
Radius (r)
5
Diameter (d)
10
Area (A)
78.5398
Circumference (C)
31.4159
Circle Formulas Reference
Key mathematical equations used to calculate circle properties from a given radius ($r$).
Diameter
$$d = 2r$$
The diameter is always twice the length of the radius.
Circumference
$$C = 2\pi r = \pi d$$
The distance around the outer boundary of the circle.
Area
$$A = \pi r^2$$
The total 2D space enclosed within the circle's perimeter.