Area of a ring between two circles. Enter the values you know and the rest are worked out, with the steps shown.
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About the annulus (ring) calculator
An annulus is the flat ring between two concentric circles, like a washer, a running track or the cross-section of a pipe. Its area is the big circle minus the small one: π(R² − r²).
Formulas
Area
K = π(R² − r²)
Width
w = R − r
Frequently asked questions
How do I find the area of a ring?
Subtract the inner circle from the outer: K = πR² − πr² = π(R² − r²).
