Software reusability is a quality attribute in which new software or its module is used with or without little modification. The benefit of reusability is that it provides reduction in development time, cost and efforts and results in increased quality and productivity. The paper demonstrates a literature review of various software reusability estimation techniques proposed by different researchers. The main objective of this paper is to find out the various factors that affect software reusability estimation. As a result of literature review we found that Neuro-Fuzzy technique can efficiently predict the level of reusability than standalone Fuzzy and Neural Network and reusability is highly dependent on Understandability, Interface Complexity, Portability, Maintainability and Customizability.