In this paper, in order to estimate an air film thickness between moving web and guide roller (web spacing height), the air film thickness formula was derived based on the finite width compressible foil bearing theory. In the derivation of air film thickness formula, the two-dimensional Reynolds equation and foil equilibrium equation were discretized by the finite difference method and solved iteratively to obtain the pressure and air film thickness distributions for various parameters. Based on the numerical results, the simplified convenience formula for the estimation of air film thickness between web and guide roller was obtained. On the other hand, the air film thickness between web and guide roller was measured by the optical sensor, and the experimental results were compared with the calculated results. Moreover, the variation of air film thickness between layer and layer in winding processes of web was analyzed by making use of the air film thickness formula. From the theoretical and experimental results obtained, the effects of air film thickness on the web transporting systems were clarified.