Circle Calculator Online

Circle Radius Diameter Area Circumference Calculator

Welcome to use circle radius diameter area circumference calculator online. A calculator of the radius, diameter, area, and circumference of a circle. Given any one variable of a circle you can calculate the other 3 unknowns.

Significant Figures

Radius Feet R = D/2

Diameter Feet D = 2R

Circumference Feet C = 2πR

Area Square Feet A = πR2

R = Radius
D = Diameter
C = Circumference
A = Area
π ≈ 3.1415926

* Units: Note that units of length are shown for convenience. They do not affect the calculations. Any other base unit can be substituted.