Relative density Definition


Relative density:


The ratio of the weight of a given volume of a substance at a given temperature to the weight of an equal volume of a standard substance at the same temperature.

For example, if 1 cubic inch of water at 39 degrees f weighs 1 unit and 1 cubic inch of another solid or liquid at 39 degrees f weight 0.95 unit, then the relative density of the substance is 0.95.

In determining the relative density of gases, the comparison is made with the standard of air or hydrogen.


The ratio of the mass of a given volume of a substance to the mass of a like volume of a standard substance, such as water or air.


The ratio of the density (mass of a unit volume) of a substance to the density of a given reference material.

Specific gravity usually means relative density with respect to water.

The term “relative density” is often preferred in modern scientific usage.