Geometry

Circle Calculator

Calculate radius, diameter, circumference, and area of a circle

How to Use
  1. Select the property of the circle you already know (Radius, Diameter, Circumference, or Area).
  2. Enter the value.
  3. Click Calculate Circle to compute all other properties simultaneously.

Formula

Circle formulas:

  • Diameter (d) = 2 × Radius (r)
  • Circumference (C) = 2 × π × Radius (r) = π × Diameter (d)
  • Area (A) = π × Radius (r)²