During the construction phase one important factor that facilitates project cost monitoring and control is the selection of the appropriate construction material suppliers. Material vendors' performance could significantly affect the project's outcome especially its final cost and schedule. This paper aims at providing a standardized approach in selecting the best supplier through the formation and use of an appropriate mathematical equation based on multiple criteria. The creation of the function is based on a prototype questionnaire survey. The participants were presented with a predefined set of criteria and were asked to rank them according to their significance. Various statistical methods and techniques were applied to the collected data that produced a number of justified results. Comparison and synthesis of the various outcomes led to the creation of the optimal function for the best supplier selection problem.