The cubic feet formula depends on the shape of the object for which one is calculating volume, but for a cube, v=a^3, where a is the length of one side in feet. For cylinders and prisms, the formula is the area of the base multiplied by the height.
Cones and pyramids also use the same formulas for determining their volumes. For both of these shapes, v=(1/3) b*h. Calculate the area of the base of a cone as a circle with a=pi*(r^2) and the base of a pyramid using the appropriate area formula for the shape.
Use caution when converting from cubic feet to cubic inches or cubic yards. One cubic foot equals 12 x 12 x 12 cubic inches, or 1728 cubic inches. A cubic foot is 1/27 of a cubic yard.