Activated carbons are widely applicable in industrial adsorption processes. However, characterization of their surface properties is problematic due to the number of different source materials and variations in production processes. Here, a model of the carbon surface derived that is based on the knowledge of fundamental molecular interactions on carbon surfaces. Adsorption isotherms of selected probe molecules are measured on different activated carbons and discussed how the model can be applied in the characterization of the surface properties of activated carbons.