The Langmuir isotherm is one of the most powerful and descriptive models for the adsorption process. Applied to fluid interfaces, in conjunction with Gibbs adsorption equation, it provides a meaningful physical description of surface tension on a molecular level. The resulting equation could be expressed as a function of volumetric phase composition or surface phase composition to calculate critical micelle concentration of surfactants in solution, as well as the adsorption and aggregation energies in a direct way, avoiding the use of empirical constants. In this work, the multiple advantages of the Langmuir model and its application to the calculation of these properties are presented.