Square the radius of the cone's base. The radius is the distance from the center of the cone's base to the edge of the cone's base. For example, if the radius equals 5 inches, square 5 to get 25 square inches.
Multiply the result by 3.14 to find the area of the base. In this example, multiply 3.14 by 25 to get 78.5 square inches.
Multiply the area of the base by the height of the cone. In this example, if the height equals 12 inches, multiply 78.5 by 12 to get 942 cubic inches.
Divide the result by 3 to find the volume of the cone. You have to divide by 3 because you are finding the area of a cone rather than a cylinder. In this example, divide 942 by 3 to get 314 cubic inches.