In this work, an improved solution for multilayer adsorption of linear species is presented. The particular case of multilayer dimer adsorption is dealt with in detail, and a new adsorption isotherm is obtained for determination of surface area and adsorption energy from experiments. From the comparison between the new isotherm and the standard Brunauer-Emmett-Teller (BET) formalism, it arises that the monolayer volume, upsilon(m) (or the surface area, A), can be up to 1.5 times larger than the one, from the BET model. The proposed model is simple and easy to apply in practice and leads to new values of surface area and adsorption heat. Physically, these advantages are a consequence of properly considering the configurational entropy of the adsorbate.