Calculator Soup^{®}
r_{1} = outer radius
r_{2} = inner radius
C_{1} = outer circumference
C_{2} = inner circumference
A_{0} = shaded area
A_{1} = area of circle of r_{1}
A_{2} = area of circle of r_{2}
π = pi = 3.14159
√ = square root
Online calculator to find the area, circumference and radii of an annulus. With any 2 known variable you can calculate the other 5 unknowns. Use the following formulas and sets of equations below.
Area of the annulus between r_{1} and r_{2}, the shaded area, is the area contained by the outer circle minus the area contained by the inner circle or A_{0} = A_{1} - A_{2}. You will need to know 2 items of information in order to calculate the remainder of variables.
* Units: Note that units of length are shown for convenience. They do not affect the calculations. The units are in place to give an indication of the order of the calculated results such as ft, ft^{2} or ft^{3}. Any other base unit can be substituted.
Outer circumference of an annulus:
C_{1} = 2πr_{1}
Inner circumference of an annulus:
C_{2} = 2πr_{2}
Surface area of the space enclosed by the outer circle
A_{1} = πr_{1}^{2}
Surface area of the space enclosed by the inner circle
A_{2} = πr_{2}^{2}
Surface area of the annulus (the gray shaded area)
A_{0} = A_{1} - A_{2}
= (πr_{1}^{2}) - (πr_{2}^{2})
= π(r_{1}^{2} - r_{2}^{2})
The following are the sets of formulas we used in our calculations:
Cite this content, page or calculator as:
Furey, Edward "Annulus Calculator" From http://www.CalculatorSoup.com - Online Calculator Resource.