Many elements in nature have three or more isotopes. One of the important separation characteristics for a gas centrifuge for multicomponent isotope separation is the overall separation factor per unit molar weight difference, gamma(o). It is desirable to estimate the value of gamma(o) for different process gases. A method of estimating gamma(o) is given in this paper. The concept of separative power of a gas centrifuge for a binary mixture is used. Finally, the parameters that influence the value of gamma(o) are shown and discussed.