Donut (Annulus) Area Calculator
Result
Donut (Annulus) Area Calculator The Donut Area Calculator finds the area of an annulus (a ring or donut shape) from its outer and inner radii, plus both circumferences. Enter the radii. — free online calculator.
Formula
- Annulus area calculator. Apply the geometric relationship below and use the worked example to verify the setup.
- The main inputs are Outer Radius, Inner Radius. Enter them in the units and format shown in the calculator.
- Keep comparable quantities in compatible units whenever the formula combines or compares them.
- Changing any input above recalculates the result with the same calculation engine used by this page.
Example: Donut (Annulus) Area
- Outer Radius: 10
- Inner Radius: 6
For R=5 and r=3: A = 16π ≈ 50.27.
Sample result: Calculating…
Frequently asked questions
What does the Donut (Annulus) Area calculate?
The outer radius R must be at least as large as the inner radius r.
Which values should I enter?
Enter Outer Radius, Inner Radius using the units and format shown beside each field.
What formula does this calculator use?
The calculator uses the following relationship: Ring area=π(R²−r²); outer circumference=2πR; ring width=R−r.
Why might my result differ from another source?
Results can differ when another source uses different units, rounding rules, conventions or assumptions. Compare the inputs and definitions before comparing results.
Does the result update automatically?
Yes. Changing an input updates the result using the same calculation engine shown on this page.