The mass transfer rate through a liquid surfactant membrane based on a film model often relies on the correct evaluation of the thickness of the membrane forming a layer around the emulsion drop. The present study gives an equation which correlates membrane thickness with the volume fraction of the dispersed hydrocarbon phase in the emulsion. The proposed equation is in good agreement with the experimental data of Goswami and co-workers [J. Membrane Sci., 54 (1990) 119] where the equation proposed by Kataoka et al. [J. Membrane Sci., 41 (1989) 197] shows deviation at higher values of microdrop holdup.