Cloud computing provides software and hardware resources in the form of cloud services with the help of internet. Cloud Computing is also coming forward as an efficient criterion for reuse. Software-as-a Service is one of the three types of cloud services which provides on demand software services on pay-as-you-go basis. In order to make SaaS more advantageous and to assist end users efficiently, there is a need to build a reusability model for SaaS. Reusability plays a very vital role in developing a product easily and efficiently. In this paper, we have proposed a software reusability estimation model for SaaS. We have been used Fuzzy Logic Methodology for evaluating the SaaS reusability. For this model, we used the SaaS reusability attributes i.e., Commonality, Accessibility, Availability, Customizability and Efficiency. Centroid Method is used for validating the results obtained from the proposed approach. This model evaluates the reusability of SaaS services with the required accuracy level. On the basis of experiment results, it has been proved out that machine learning techniques gives enhanced accuracy of estimation as compared to other reusability estimation techniques, found helpful and more useful for SaaS service providers as well as users.