Assuming that the density of a substance is Xg/ml, the formula for calculating the volume of this substance is V= 1/X(ml), and 1g is equal to 1ml. Gram is the unit of weight, and milliliter is unit of volume, which is difficult to convert. Gram, the unit of mass, is marked as g. One gram is the mass of18 *14074481c-12 atom. The weight of one gram is equivalent to about one cubic centimeter of water at room temperature.