The manpower planning models available in literature have dealt with how changes takes place in a manpower planning system, under various operating and policy constraints. However none of these models have identified the manpower system costs. In this paper we have identified various manpower system costs. Further, we have developed a manpower planning model with the objective of minimizing the manpower system costs. The model has been found to be analogous to Wagner-Within model in Production/Inventory management. A numerical illustration has been given to validate the model.