The theoretical calculations were evaluated for thirty four drug compounds. Many parameters have been calculated theoretically and enter as a model to predicting the best values of practical (Log P). All these compounds were evaluated by semi-empirical (AM1) and Hartree Fock in basis set (HF/STO-3G) using Gaussian 03w. The thermodynamic descriptors like HOMO, LUMO, total energy, Gibbs Free Energy etc were computed and played an important role for predictions the practical lipophilicity values. A linearity was shown when correlated with experimental data. Multiple linear regression analysis was performed to derive quantitative structure activity relationship models which were further evaluated for the predictions.