A circle does not measure in cubic yards because cubic yards refers to volume while a circle only has area. However, a sphere, which is a three-dimensional circle, does have volume that can be quantified in cubic yards. To find the volume of a sphere or the area of a circle, you need to know the radius. The radius measures the distance from the center of the circle or sphere to the outside of the circle or sphere. Since circles and spheres are perfectly round, it does not matter which point on the shape you measure to; the radius will always be the same.
Area of a Circle
Measure the radius of the circle with a ruler.
Square the radius. For example, if the radius equals 3 yards, multiply 3 yards by 3 yards to get 9 square yards.
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Multiply the result by pi, approximately 3.14, to find the area of a circle. Completing the example, multiply 9 square yards by 3.14 to find the area of the circle equals 28.26 square yards.
Volume of a Sphere
Cube the radius of the sphere. To "cube" a number means to multiply it by itself, and then do it again. For example, if the radius equals 3 yards, multiply 3 yards by 3 yards to get 9 square yards, then multiply 9 square yards by 3 yards to get 27 cubic yards.
Multiply the result by pi, approximately 3.14. In this example, multiply 27 cubic yards by 3.14 to get 84.78 cubic yards.
Multiply the result by 4/3 to find the volume of the sphere in cubic yards. Completing the example, multiply 84.78 by 4/3 to get 113.04 cubic yards.