# Specific Gravity of Soil

Written by Jerry Ratzlaff on . Posted in Geotechnical Engineering

Specific gravity of soil, abbreviated as $$SG_s$$, a dimensionless number, the mass of solids in the soil compared to the mass of water at the same volume.

## Specific Gravity of soil formulas

$$\large{ SG_s = \frac{ \rho_s }{ \rho_w } }$$

$$\large{ SG_s = \frac{ M_s }{ V_s \; \rho_w } }$$

$$\large{ SG_s = \frac{ W_s }{ V_s } \; \gamma_w }$$

Symbol English Metric
$$\large{ SG_s }$$ = specific gravity of soil $$\large{dimensionless}$$
$$\large{ \rho_s }$$  (Greek symbol rho) = density of soil $$\large{ \frac{lbm}{ft^3} }$$ $$\large{ \frac{kg}{m^3} }$$
$$\large{ \rho_w }$$  (Greek symbol rho) = density of water $$\large{ \frac{lbm}{ft^3} }$$ $$\large{ \frac{kg}{m^3} }$$
$$\large{ M_s }$$  = mass of soil $$\large{lbm}$$ $$\large{kg}$$
$$\large{ \gamma_w }$$  (Greek symbol gamma) = unit weight of water $$\large{ \frac{lbm}{ft^3} }$$ $$\large{ \frac{N}{m^3} }$$
$$\large{ V_s }$$ = volume of solid soil $$\large{ft^3}$$ $$\large{m^3}$$
$$\large{ W_s }$$ = weight of soil $$\large{lbf}$$ $$\large{N}$$