How to Calculate the Volume of a Cone
To calculate the volume of a cone, start by finding the cone's radius, which is equal to half of its diameter. Next, plug the radius into the formula A = πr^2, where A is the area and r is the radius. Once you have the area, multiply it by the height of the cone. Finally, divide that number by 3 to find the volume of the cone. Remember to write your answer in cubic units.
Find the radius. If you already know the radius, then you can move on to the next step. If you know the diameter, divide it by 2 to get the radius. If you know the circumference, divide it by 2π to get the diameter. And if you don't know any of the measurements of the shape, just use a ruler to measure the widest pie circular base (the diameter) and divide that number by 2 to get the radius. Let's say the radius of this cone's circular base is.5 inches (1.3 cm). Use the radius to find the area of the base circle. To find the area of the base circle, you can just use the same formula you'd use to find the area of a circle: A = πr. Plug ".5" in for r to get A = π(.5) and square the radius and multiply it by the value of π to find the area of the circular base. π(.5) =.79 in.. Find the height of the cone. If you know it already, write it down. If you don't know it, use a ruler to measure it. Let's say the height of the cone is 1.5 inches (1.3 cm). Make sure that the height of the cone is written in the same measurements as the radius. Multiply the area of the base by the height of the cone. Multiply the area of the base,.79 in. , by the height, 1.5 in. So,.79 in. x 1.5 in = 1.19 in. Divide the product by three. Simply divide 1.19 in. by 3 to find the volume of a cone. 1.19 in. /3 =.40 in.. Always state the volume in cubic units because it's a measure of three-dimensional space. 
Find the radius. Use the radius to find the area of the base circle. Find the height of the cone. Multiply the area of the base by the height of the cone. Divide the product by three. 