The successful development of the ideal adsorbed solution theory to estimate multicomponent adsorption equilibria for systems such as granular activated carbon-dilute aqueous solution of organics has necessitated the formulation of algorithms which incorporate the IAS theory in adsorption calculations. Although the IAS theory defines the equilibrium relation not by explicit expressions but through a system of equations, this apparent difficulty does not prove to be insurmountable. The procedures established in this work cover the situations most likely encountered in adsorption calculations, in which the use of the equilibrium relationship is invoked.