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 Calculator

Outer Radius (R) or     Diameter
Inner Radius (r) or     Diameter
annulus area

Annulus Area Formula

The annulus area formula is

π (R2 - r2)


R = outer radius of a circle.
r = inner radius of a circle.
π ≈ 3.1415926.


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

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