Circle Calculator

Choose a Calculation:
r =  Units:
   
   

A = 
C = 

Circle Geometric Shape

Circle Geometric Shape with Radius
r = radius
A = area
C = circumference
Π = Pi

Circle Formulas in terms of radius r: (Π = Pi)

Area of a circle:

A = Π * r2

Circumference of a circle:

C = 2 * Π * r

Circle Calculations:

Use the following additional formulas along with the formulas above.

  • Given the radius of a circle calculate the area and circumference
    Given r find A, C
    • use the formulas above
  • Given the area of a circle calculate the radius and circumference
    Given A find r, C
    • r = √(A / Π)
    • C = 2 * Π * r
  • Given the circumference of a circle calculate the radius and area
    Given C find r, A
    • r = C / 2Π
    • A = Π * r2
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