A new approach is presented to estimate molar volumes and densities of liquids in ambient conditions from van der Waals models, taking advantage of the correlation between the intermolecular volume and the atomic contributions to the molecular surface area. Using this approach, the role of hydrogen bonds can be quantified. The densities obtained prove remarkably close to the values derived from the ACD group contribution method. However, the present approach requires much less empirical parameters and may be applied to arbitrary H-C-N-O-F-S-Cl-Br compounds. Moreover, it is more reliable than earlier empirical procedures, including quantitative structure property relationships (QSPR). While it does not correct the deficiencies of group contribution methods, it provides a natural approach to introduce temperature effects.