An annulus is a geometric shape that is formed by two concentric circles. The Annulus Calculator is an online tool that helps you calculate the area, circumference, and radii of an annulus. With any two known variables, you can calculate the other five unknowns.
Concepts
An annulus is a two-dimensional shape that consists of two concentric circles. The outer circle has a larger radius than the inner circle. The area of an annulus is the difference between the area of the outer circle and the area of the inner circle. The circumference of an annulus is the sum of the circumference of the outer circle and the circumference of the inner circle.
Formulae
The following formulae are used to calculate measures of an annulus:
- Outer circumference of an annulus:ย
C1 = 2ฯr1
- Inner circumference of an annulus:ย
C2 = 2ฯr2
- Surface area of the space enclosed by the outer circle:ย
A1 = ฯr1^2
- Surface area of the space enclosed by the inner circle:ย
A2 = ฯr2^2
- Surface area of the annulus (the gray shaded area):ย
A0 = A1 - A2 = ฯ(r1^2 - r2^2)
Benefits
The Annulus Calculator provides a quick and easy way to calculate measures of an annulus. It can be used in various fields such as engineering, architecture, and mathematics. It saves time and effort by eliminating manual calculations.
Interesting Facts
- The word โannulusโ comes from Latin and means โringโ.
- The area of an annulus can also be calculated using Greenโs theorem.
- The Annulus Calculator can be used to calculate measures of other shapes such as torus and circular sector.
Use Cases
The Annulus Calculator can be used in various fields such as:
- Engineering: It can be used to calculate measures of annular seals, gaskets, and bearings.
- Architecture: It can be used to calculate measures of circular windows, doors, and skylights.
- Mathematics: It can be used to teach students about geometric shapes and their properties.
References
- 3ย Kostov, Vasil. โOn the Area Formula for Annuli.โ Journal of Geometry 107, no. 1 (2016): 119-26. https://doi.org/10.1007/s00022-015-0297-y

Emma Smith holds an MA degree in English from Irvine Valley College. She has been a Journalist since 2002, writing articles on the English language, Sports, and Law. Read more about me on her bio page.