Equation for the Volume Volume can be simply defined as the space occupied by a 3D object. Often, we need to know how much of a solid, liquid, or gaseous matter can be placed within a container. Suppose you want to know how much soda can be filled in a cylindrical can of certain measurements. If you know how to calculate the volume of a cylinder, you instantly get your answer. Hence volume calculations are important in our day-to-day lives. A cylinder is a three dimensional geometric figure. It has a rounded surface, and is bound by two circular surfaces on its top and bottom. The formula for the area of a circle is πr². But a cylindrical surface has a height. Hence, by combining both these parameters, the formula for the volume of a cylinder is: πr²h, where "r" is the radius of the two circles on each side of the cylinder, and "h" is the cylinder's height. Calculations Suppose, you have a cylinder whose radius is 10 in and height is 14 in. Simply substitute the values in the above mentioned formula: πr²h = 22/7 * 10² * 14 = 4400 in³. The unit for denoting the volume is written as the cube of the measured units. In the above example, both measurements are in inches, the volume unit will be "in³ or cubic inches". As it is a 3D object, the denotation of "cubic" is written in the unit. Now, how to measure the volume in gallons? One US gallon is 231 cubic inches. Hence, by dividing the result by 231, you get the volume in gallons. 4400 in³/231 = 19.0476 gallons. This means that a cylinder that has a radius of 10 inches and a height of 14 inches, will hold approximately 19 gallons of a liquid.