Porosity, saturation, and density are related as a function of porosity F as:

                                                                (1)

In which subscripts f and m refer to the formation and the matrix densities (s), respectively, and S is the fractional water saturation.  A water density of 1,000 kg/m³ is assumed. 

The pages found under Properties are substantially based on a report produced by the United States Department of Transportation:

Wightman, W. E., Jalinoos, F., Sirles, P., and Hanna, K. (2003). "Application of Geophysical Methods to Highway Related Problems." Federal Highway Administration, Central Federal Lands Highway Division, Lakewood, CO, Publication No. FHWA-IF-04-021, September 2003. http://www.cflhd.gov/resources/agm/