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Annulus Calculator

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


Annulus Calculator: An Annulus is a ring shaped object (the area between two concentric circles). This image shows an annulus shape with associated calculations used by the Annulus Calculator

Dimension Outer Inner Comments
Diameter D1 mm D2 mm D1=Outside diameter D2=Inside diameter
Radius r1 mm r2 mm The Radius is the distance between the centre of a circle and its edge
Circumference C1 mm C2 mm The Circumference is the distance around a circle.
Area A1 sq.mm A2 sq.mm These areas shown for reference
Area of Annulus sq.mm Calculated by subtracting the area based on the outside diameter from the area based on the inside diameter.
width W mm Calculated by dividing the difference between the outside and inside diameters by two.

You can refine the calculations by controlling the number of decimal places that the calculator calculates to. The default is 2 decimal places.

This calculator includes the following algorithms

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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