A convenient method for estimating van der Waals cross-sectional surface areas was developed using a molecular modeling program. Relative and absolute (argon reference) cross-sectional areas for 105 compounds were determined and compared by regression analysis with areas obtained by adsorption methods on various adsorbent surfaces. A plot of the entire set of 105 different compounds yielded a slope of 0.946 and a correlation coefficient, r; of 0.885. Excellent correlation is realized between calculated and experimental areas when the comparison is limited to graphitized carbon as the adsorbent and adsorbates are limited to n-alkane, branched alkane, and cyclic alkane compounds (slope = 1.010 and r = 0.974). Correlations were also found from subsets of data for varied adsorbents and adsorbates including alkanes, alkenes, aromatics, noble gases, alkyl halides, amines, and alcohols.