The growth of Thailand s real estate and the limit of construction time need to use post-tensioning prestress concrete slab, especially in a large construction project. Because of its nature of engineering-to-order, specifications of a post-tension slab in each project are different. As a result, a factory manufacturing strand for a post-tension slab meet production planning problem whereas weight of strand used in each project cannot be determined until a design process is completed. This problem is not only inefficiency of workforce and underutilization of machines in the factory, but also causes changes in the production plan. Therefore, we studied the information flows after the sale completion to the beginning of production and applied principles of forecasting to estimate quantities of stand for developing master production schedule. This proposed forecasting is a linear regression model using engineering information available before the design stage as factors to predict ratio of stand to area. The analysis of regression model shows that the main regression factors are maximum column span, size of band beam, slab thickness, and super imposed dead loads. The validation of model using a different data shows that Mean Average Percentage Error (MAPE) are 8.6 in terms of ratio of strand to area.