Online Calculators > Math Calculators > Annulus Calculator Annulus Calculator
Annulus Calculator calculates the area of an annulus by knowing its outer radius or diameter and inner radius or diameter.
Annulus Area Formula
The annulus area formula is
π (R^{2}  r^{2})
where
R = outer radius of a circle.
r = inner radius of a circle.
π ≈ 3.1415926.
Example
For example,
if the outer radius is 10, and the inner radius is 5.
The area is calculated as
A = π x (R^{2}  r^{2})
= 3.1416 x (10 x 10  5 x 5)
= 3.1416 x 75
= 235.62
