Annulus

The area between two concentric circles.

Annulus formula

\(\large{ A= \pi \;r_{id}^2 - \pi \; r_{od}^2 }\)

\(\large{ A= \pi \; \left( r_{id}^2 - r_{od}^2 \right) }\)

Where:

\(\large{ A }\) = area

\(\large{ \pi }\) = Pi

\(\large{ r_{id} }\) = radius (inside diamester)

\(\large{ r_{od} }\) = radius (outside diameter)