A cubic foot is a unit of measure that represents volume, or how much space a solid figure occupies. It is easy to calculate cubic feet of a cube but you can also easily determine the cubic feet of a sphere or cylinder. The equation for the volume of a cube is length x width x height, while the equation for the volume of a sphere is 4/3 π(radius^3); the volume of a cylinder can be determined by the equation height x π(radius^2).
For a Cube
Determine the length of your cube in feet.
Find the width of your cube in feet.
Figure out the height of your cube in feet.
Multiply the results of steps 1, 2 and 3. It does not make a difference in what order you multiply the numbers. For example, if the length, width, and height of your cube is 10, 12 and 14 feet, respectively, then the volume of the cube is 10 x 12 x 14, which equals 1,680 cubic feet.
For a Sphere
Determine the radius of your sphere in feet. Radius is the distance from the center to the surface of the sphere. Find the cubed value of the radius or the radius to the third power. For example, if your radius is 3 feet, then the radius to the third power is 27 cubic feet.
Multiply the result of step 1 by pi, which is a constant that approximately equals 3.14. Using the example from step 1, multiplying 27cubic feet by 3.14 is 84.78 cubic feet.
Multiply the result of step 2 by 4/3. Continuing the example from step 2, multiplying 84.78 cubic feet by 4/3 equals 113.04 cubic feet.
For a Cylinder
Determine the radius of circular face of the cylinder in feet. The radius is the distance from the center of the circular face to the edge of the circle. Square the radius. For example, if the radius is 2 feet, then the squared value is 4 square feet.
Multiply the result of step 1 by pi (3.14). Using the example from step 1, 4 square feet multiplied by 3.14 is 12.56 square feet.
Determine the height of the cylinder and multiply by the result of step 2. For example, if the height of the cylinder used in step 2 is 10 feet, then multiplying this by the result of step 2 yields a volume of 125.6 cubic feet.