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 (R² - r²)

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 (R² - r²)
= 3.1416 x (10 x 10 - 5 x 5)
= 3.1416 x 75
= 235.62