What is the specific gravity of water

The Relative density d, also specific density, describes the relationship between two densities or weights.

  • the ratio of the density ρ of a substance to the density ρ0 one Normal condition of this substance
  • the density ρ of a substance to the reference density ρ0 one Upholstery fabric

As a size ratio, the relative density is a dimensionless quantity without a unit. The density itself is Mass per volume (Unit: kg / m³), ​​the Weights (which also specific weight is called) Weight force per volume (Unit: N / m³). This difference is defined in DIN 1306.

Reference values

Common standard reference densities (Normal) are the density of pure water under normal conditions at 3.98 ° C and the density of dry air under normal conditions (0 ° C and 1013.25 mbar = 1.2931 kg / m³) or standard conditions (20 ° C or 25 ° C, same air pressure).

There are also references to the material itself under normal or standard conditions


In mineralogy and engineering, density information is mostly related to the density of water. The use is useful when a material is e.g. B. as a result of different temperatures in different structures, e.g. B. is present with greater or lesser porosity.

It is also used to compare specific energies (such as the calorific value) of different substances, including in DIN 1871 Gaseous fuels and other gases, density and relative density based on the standard condition (May 1980) treated.


  • DIN 1306 Density; Terms, information
  • Bergmann, Schaefer: Experimental Physics Textbook, Volume 1, 11th edition

Category: substance property