Annulus Area
An annulus is the ring left after removing a concentric smaller disk. Its area is the difference of two circle areas.
Annulus Area
Circles · 2 inputs
How to use this calculator
- Enter outer radius in cm.
- Enter inner radius in cm.
- Select Calculate and keep the output unit with the answer.
Before you use the answer
Start with a dimensioned sketch and label the units beside every measurement. Distinguish the outer edge from an internal opening, and distinguish a radius from a diameter. A geometric model is most useful when the shape actually matches the assumptions in the formula.
The outer radius must exceed the inner radius. The centres are assumed to coincide.
Does it save my inputs?
No calculation history is stored by this website. The calculator works locally in your browser. See the privacy policy for hosting and contact details.
Why might a result be approximate?
Measurement uncertainty, ideal-model assumptions and floating-point rounding can all matter. Displaying more digits does not improve the original measurement.
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