Specific gravity is the density of a material relative to water. Water has a specific gravity of 1.0, so a material at 0.85 is lighter than water and one at 1.2 is heavier - the figure is a ratio, with no units.
It is one of the most commonly measured properties in chemical manufacturing because it is quick, cheap and informative. Measuring it takes minutes with simple equipment, and because a formulation's specific gravity depends on what is in it, a reading outside expectation is a fast signal that something is wrong - a component omitted, over-added, or a wrong material used. It is a routine in-process check for that reason.
It also matters commercially, because chemical products are frequently sold by volume but priced or shipped by weight. Converting between the two requires specific gravity, and getting it wrong misstates both cost and freight. It is equally necessary for filling by weight into containers sized by volume.
Specific gravity varies with temperature, since materials expand when heated, so a specification should state the temperature at which the figure applies. It typically appears alongside viscosity and appearance on a certificate of analysis.
Confirm whether your product is being sold and priced by weight or by volume, and that both parties are using the same specific gravity to convert. It is a small detail that produces meaningful errors in cost and freight calculations. It is a useful in-process check to have written into the process specification as well, since catching a charging error before the batch is completed costs far less than discovering it at release testing.
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Last reviewed: August 2026. Regulation and guidance change — verify anything you rely on against the primary source. Tell us if something here is out of date.
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