This paper shows the application of "Wagner-Whitin" algorithm, that seeks to find the best inventory restocking in a Project-based system. The capacity and supply cost parameters by type of material is considered. The model reduces supply costs and ensures the availability of materials at each stage of the project. The planning of engineering project activities and material requirements are used as input data.The combined algorithm is applied, resulting in the lowest system cost, and the scheduling of supplies by the provider for each required period.