How to Calculate Specific Gravity

Specific Gravity is the ratio of the density of a soil to the density of water.

$latex SG = \frac{\rho_s}{\rho_w}&s=2$
Where:
SG = Specific Gravity (dimensionless)
ρ_s = bulk density of soil (kg/m³ or lb/ft³)
ρ_w = bulk density of water (kg/m³ or lb/ft³)
= 1000 kg/m³ (62.4 lb/ft³)

Specific Gravity of Various Substances

Relative Density

Relative Density is related to Specific Gravity in that it compares the density of a substance to a certain reference density rather than that of water.