The networks-on-chip(NOC) approach was proposed as a promising solution to on-chip communication problems, but it is by far more resource limited. The input buffers in a typical on-chip router take a significant portion of the silicon area of NOC, and the performance of a NOC is drastically affected by the amount of buffering resources. In this paper, an application-specific buffer planning algorithm that can be used to customize the router design in NOC is presented. More precisely, given the mapping of the target application and the traffic characteristics, the algorithm automatically assigns the buffer depth for each input channel, in different routers across the chip. The experimental results show that the system buffering resources can be utilized more effectively. In contrast with the uniform buffer allocation, about 50% saving in buffering resources can be achieved by automatic buffer allocation using our algorithm without any reduction in performance.