Polymers typically have a "specific" density that can provide an approximation of the density of a particular material. However, various factors can affect the density, such as crystallinity, loss of softener or solvent absorption. Components of the same sample may also vary in density due to differences in crystallinity, thermal history, porosity, or changes in material composition, such as the addition of a filler or pigment. The variety of properties of most engineering polymers causes differences in their applications. This can cause variety in density of polymers. In fact, many polymers are identified and classified by this important factor. Like all tests, this test also has uncertainties, and in this article, an attempt has been made to describe the important factors that cause errors and uncertainties in this test method