A typical LFER relation for predicting the equilibrium concentration of a compound or solute in the vapor phase to a condensed (or solvent) phase can be defined as follows (following M.H. Abraham and co-workers):
where  is some free-energy related property, such as an adsorption or absorption constant, , anesthetic potency, etc. The lowercase letters (, , , , ) are system constants describing the contribution of the aerosol phase to the sorption process. The capital letters (, , , , ) are solute descriptors representing the complementary properties of the compounds. Specifically,
*  is the gas–liquid partition constant on n-hexadecane at 298 K;
*  = the excess molar refraction ( for n-alkanes).
*  = the ability of a solute to stabilize a neighbouring dipole by virtue of its capacity for orientation and induction interactions;
*  = the solute's effective hydrogen bond acidity; and
*  = the solute's effective hydrogen-bond basicity.
The complementary system constants are identified as
*  = the contribution from cavity formation and dispersion interactions;
*  = the contribution from interactions with solute n-electrons and pi electrons;
*  = the contribution from dipole-type interactions;
*  = the contribution from hydrogen-bond basicity (because a basic sorbent will interact with an acidic solute); and
*  = the contribution from hydrogen-bond acidity to the transfer of the solute from air to the aerosol phase.
Similarly, the correlation of solvent–solvent partition coefficients as , is given by
where  is McGowan's characteristic molecular volume in cubic centimeters per mole divided by 100.