How to Calculate Annulus
What is Annulus?
An annulus (ring) is the region between two concentric circles — an outer circle of radius R and an inner circle of radius r. It appears in engineering (pipe cross-sections), design, and optics.
Step-by-Step Guide
- 1Determine the outer radius R and inner radius r
- 2Area = π(R² − r²)
- 3Outer circumference = 2πR, inner circumference = 2πr
- 4Width of the ring = R − r
Worked Examples
Input
R=10, r=6
Result
Area = 201.06 units²
π(100−36) = 64π
Input
R=5, r=3
Result
Area = 50.27 units²
π(25−9) = 16π
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