Annulus Area Calculator
Compute the area of an annulus (ring) from the outer and inner radii.
About Annulus Area Calculator
An annulus is the region between two concentric circles. Its area is the difference of the two circle areas: π(R² − r²).
Formula
Annulus Area
A = π(R² − r²)
- R
- Outer radius
- r
- Inner radius
Worked example
With the default values below, Annulus Area Calculator returns Annulus Area of 201.0619. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Outer Radius (R)minimum 0 units
- 10 units
- Inner Radius (r)minimum 0 units
- 6 units
Results
- Annulus Area
- 201.0619 sq units
Step by step
- 1Apply annulus formula= 201.0619
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What if the inner radius is zero?
Then the annulus becomes a full circle with area πR².
Can I use diameter instead of radius?
Yes — divide each diameter by 2 to get the corresponding radius, then apply the formula.