Annulus Area Calculator
An annulus is the ring-shaped region between two concentric circles. Its area is the outer disk area less the inner disk area.
How to use this calculator
- Enter the values requested by the Annulus Area and keep all units consistent.
- Check the formula and worked example before relying on the displayed result.
- Change one input at a time when comparing alternative scenarios.
Formula and method
A = π(R² − r²)
- The calculator applies the stated relationship to the inputs entered by the visitor. Intermediate calculations use full numeric precision before display rounding.
- Enter radii rather than diameters; the inner radius cannot exceed the outer radius.
Worked examples
Worked example: Annulus Area
Outer radius 5 and inner radius 3 units
A = π(25 − 9) = 16π ≈ 50.27 square units.
A = π(25 − 9) = 16π ≈ 50.27 square units.
Understanding the result
Use the output as a calculation for the chosen assumptions, not as an explanation of why a real-world result occurred.
Enter radii rather than diameters; the inner radius cannot exceed the outer radius.
Important notes
Enter radii rather than diameters; the inner radius cannot exceed the outer radius.
Confirm the units, source measurements, rounding convention and context before using the result for a real project or decision.
Frequently asked questions
What does this Annulus Area calculate?
An annulus is the ring-shaped region between two concentric circles. Its area is the outer disk area less the inner disk area.
Which assumptions matter most?
Enter radii rather than diameters; the inner radius cannot exceed the outer radius.
Can the result replace professional or domain-specific guidance?
No. The tool provides arithmetic under its stated assumptions; check applicable specifications, accounting conventions, standards or qualified guidance for consequential decisions.
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Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.