Specific Gravity (SG) is the ratio of the density of the substance to a reference density, usually deionized water. In other words, it is the ratio of the mass of the substance to that of a reference mass for the same given volume at room temperature. Being a ratio of densities, specific gravity is a dimensionless quantity but varies with temperature and pressure. For this reason, it is crucial that densities of the sample and reference are determined at the same temperature and pressure.

Test Method A as per ASTM D792-08 is used to determine the specific gravity and density for polymers. This test method uses water as the immersion liquid and an electronic single pan balance.

Calculate the specific gravity of the plastic as follows:

sp gr 23/23°C = a/(a + w – b)


a = apparent mass of specimen, without wire or sinker, in air,

b = apparent mass of specimen (and of sinker, if used) completely immersed and of the wire partially immersed in liquid, and

w = apparent mass of totally immersed sinker (if used) and of partially immersed wire.


Related Standards

  • Environmental Protection Agency
  • European Union
  • Food & Drug Administration
  • ICH Q3D
  • International Council for Harmonisation
  • International Organization for Standardization

We are passionate about your success. Tell us more about your regulatory and quality needs to learn about how we can help.

Book a Consultation


To display custom copy instead of global copy in this section, please go to Show Global Content for Bottom CTA? toggle in the "Contents" tab to the left, toggle it off, save, and then REFRESH the page editor, the custom text will then show up and ready to be edited.

Turning the global content back on will be the same process, go to the toggle and toggle it back on, save and refresh!