The relationship
Formula
A = π(R² − r²) · width = R − r
For outer radius 10 cm and inner radius 6 cm: area ≈ 201.0619 cm² and radial width = 4 cm.
Rings & washers
Annulus & Ring Area Calculator
An annulus is the ring between two concentric circles. Enter the inner and outer size to get material area, ring width and both edge lengths.
FreeNo sign-inInstant results
INPUT
Size the inner and outer circles
Use either radii or diameters consistently.
RESULT
Calculated instantly
Ring area201.0619 cm²
Radial width4 cm
Outer circumference62.8319 cm
Inner circumference37.6991 cm
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Straight answers
Common questions
What is an annulus?
An annulus is the flat ring-shaped region between two circles that share the same center.
Can I enter inner and outer diameters?
Yes. Select diameter mode and the calculator converts both values to radii before calculating.
How do I find ring width?
Subtract the inner radius from the outer radius. In diameter mode, the calculator handles the halving automatically.