Specific Gravity (Relative Density)
Specific Gravity - SG - is a dimensionless unit defined as the ratio of the density of a substance to the density of water - at a specified temperature, and can be expressed as
SG = ρsubstance / ρH2O (3)
SG = Specific Gravity of the substance
ρsubstance = density of the fluid or substance (kg/m3)
ρH2O = density of water - normally at temperature 4 oC (kg/m3)
It is common to use the density of water at 4 oC (39oF) as a reference since water at this point has its highest density of 1000 kg/m3 or 62.4 lb/ft3.
Specific Gravity - SG - is dimensionless and has the same value in the SI system and the imperial English system (BG). Water is normally also used as reference when calculating the specific gravity for solids.
- Thermal Properties of Water - Density, Freezing temperature, Boiling temperature, Latent heat of melting, Latent heat of evaporation, Critical temperature ...
Specific Gravities for some common Materials
- SG -