Circle Calculator

Calculate all circle properties from any known value: radius, diameter, circumference, or area.

Input Value

I know the

Radius

Enter the radius of the circle

Circle Formulas

Circumference

C = 2πr = πd

Area

A = πr² = π(d/2)²

Relationships

d = 2r

r = C / 2π = √(A / π)

Related Calculators

Calculate area, perimeter, angles, and sides of any triangle given known values.

Solve right triangles - find missing sides and angles using trigonometry.

Calculate the missing side of a right triangle using a² + b² = c².

Circle Properties

Radius5

Diameter10

Circumference31.4159

Area78.5398

Visualization