Annulus Calculator

Annulus (Ring) Calculator

Calculate the area of a ring (annulus) between two concentric circles. Simply enter the outer and inner radius.

Outer Radius (R)

Inner Radius (r)

Unit

Annulus Area Formulas

Difference between two concentric circles

A = \pi(R^2 - r^2)

Using the average radius and width

A = \pi(R+r)(R-r)

Large circle area minus small circle area

A = \pi R^2 - \pi r^2

An annulus is the region between two concentric circles (circles that share the same center). It looks like a ring or a washer.

Real-world examples: Washers, CDs/DVDs, donuts, tire treads, circular race tracks, pipe cross-sections

R (Outer Radius):Distance from center to outer edge

r (Inner Radius):Distance from center to inner edge

Width:w = R - r

Calculate full circle area

Calculate arc length and sector area

Learn about circle properties