How does the Annulus Calculator work?

Determine the outer radius R and inner radius r Then: Area = π(R² − r²) Then: Outer circumference = 2πR, inner circumference = 2πr Then: Width of the ring = R − r.

Can you give an example of how to use the Annulus Calculator?

Example: Input R=10, r=6 gives a result of Area = 201.06 units² (π(100−36) = 64π).

Is the Annulus Calculator free to use?

Yes — completely free with no registration, download, or subscription required. All calculations happen instantly in your browser.

How accurate is the Annulus Calculator?

Our Annulus Calculator uses verified mathematical formulas and is accurate to multiple decimal places. Results are calculated in real-time using the same methods used by professionals.

Mathematics

Annulus Calculator

Annulus Area Calculator

Outer Radius (R)

Inner Radius (r)

Annulus = ring between two concentric circles. R must be greater than r.

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.

Property	Formula
Area	A = π(R² − r²)
Outer circumference	C₁ = 2πR
Inner circumference	C₂ = 2πr
Width	w = R − r

References

›Annulus — Wikipedia

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Annulus Calculator

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Annulus Formulas

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Annulus Area Calculator