### How to Calculate the Specific Gravity of a Substance

By Steven Holzner . In physics, a substance''s specific gravity is the ratio of that substance''s density to the density of water at 4 degrees Celsius. Because the density of water at 4 degrees Celsius is 1,000 kg/m 3, that ratio is easy to example, the density of gold is 19,300 kg/m 3, so its specific gravity