Specific Gravity (relative density) calculator
Calculator
Theory
Specific gravity (also called relative density) is the ratio of the density ( ρ ) of a substance to the density of another reference substance at
a given specified conditions:
Specific gravity for liquids and solids is usually measured with respect to water at 4ÂșC (or 39.2ÂșF). Density of water at 4ÂșC is 1000 kg/m
3 or 1 g/cm
3.
Specific gravity of gases is defined by:
SG = Molecular Weight of Gas / Molecular Weight of Standard Air
(Molecular weight of dry air is 28.96469)
whereas relative density is:
ρr= Density of Gas / Density of Air (at the same temperature and pressure)
For gases the reference usually is air at room temperature (20ÂșC or 68ÂșF) and a pressure of 101.325 kPa absolute. Density of air at 20ÂșC and 1 atm (101.325 kPa) is 1.205 kg/m
3.
If compressibility factors are not considered: ρ
r= SG.
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