Online Calculators since 2009
An Annulus is a ring shaped object (the area between two concentric circles)
Enter the dimensions of the outer and inner circles to calculate the annulus.
There is an option to create a PDF document from the details entered
Diameter is the Radius x 2
Radius is the Diameter x 0.5
Circumference is PI x Diameter
Area is 2 x PI x Radius
PI is 3.141592654 (to 9 decimal places)
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