Calculate area, circumference, and width of a ring-shaped annulus.
Doughnut Dimensions
Annulus Results
235.62
Total Area
Geometric properties of the circular ring.
Ring Width5.00
Outer Circumference62.83
Inner Circumference31.42
About this calculator
What is an Annulus?
The term 'annulus' comes from the Latin word for 'little ring'. In geometry, it is the region bounded by two concentric circles of different radii. You can think of it as a 2D doughnut or a washer.
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Pro Tips
The outer radius (R) must always be larger than the inner radius (r).
The width of the annulus is simply R - r.
If the inner radius is 0, the annulus becomes a standard circle.
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Fun Facts
"Solar eclipses can be 'annular' when the Moon doesn't completely cover the Sun, leaving a visible 'ring of fire'."
"Mechanical washers are simple physical examples of an annulus designed to distribute pressure."
"The pipes and tubing used in plumbing are essentially 3D extensions of an annulus!"
