A key issue in MANETs is the necessity that the routing protocols must be able to respond rapidly to topological changes in the network. At the same time, due to the limited bandwidth available through mobile radio interfaces, it is essential that the network traffic, generated by the routing protocols should be kept at a minimum. Several protocols exist, addressing the problems of routing in mobile ad-hoc networks. MANET routing protocols are designed to adaptively cater to dynamic changes in topology while maximizing the throughput and packet delivery ratio, and minimizing delay, aggregate good put, average jitter and minimum packet loss. In this paper a simulative study on MANET routing protocols aims to determine its packet delivery ratio performance with respect to simulation time, packet size & mobility.