This circle calculator finds the area, circumference or radius of circles by considering a given variable that should be provided (area or diameter or circumference).


Circle formulas

  • Radius and diameter:

r = d/2

  • Area of a circle formula:

A = πr2 = πd2/4

  • Circumference of a circle:

C = 2πr = πd


A = area
C = circumference
r = radius
π = pi = 3.14159
√ = square root

How does this circle calculator works?

Depending on what figure needs to be calculated this circle calculator requires to input only one circle variable as explained here:

  • In case the radius (r) value of a circle is provided it will calculate its area (A) and circumference (C ) by using these two equations:

A = πr2

C = 2πr

  • If the circle area (A) is known it will determine its radius (r) and circumference (C):

r = √(A / π)

C = 2πr

  • By giving the circumference (C) of a circle it will compute its area (A) and radius (r):

r = C/2π

A = πr2

16 Apr, 2015