Path duration is an important design parameter that determines the performance of a mobile ad hoc network (MANET). For example, it can be used to estimate the route expiry time parameter for routes in “on demand” routing protocols. This paper proposes an analytical model to estimate path duration in a MANET using the random way point mobility model as a reference. The salient feature of the proposed model is that it establishes a relationship between path duration and MANET design parameters including node density, transmission range, number of hops, and velocity of nodes. Although this relationship has been previously demonstrated through simulations, a detailed analytical model is not available in the literature to present. In particular, the relationship between path duration and node density has not been derived in previous models. The accuracy of the proposed model is validated by comparing the results obtained from the analytical model with the experimental results available in literature and with the results of simulations carried out in ns-2.