This paper establishes a vigorous methodology, based on the fuzzy set theory, to improve the facilities layout process that has occupied scholars and practitioners for more than four decades. Fuzzy set theory is an appropriate tool which uses the natural language that humans use to control complex systems such as facilities planning. The closeness rating between departments in a plant depends on qualitative and quantitative factors. Some of these factors may have greater effect on the designer's decisions about such ratings. Thus, the pairwise comparison of the analytical hierarchy process (AHP), which ensures the consistency of the designers' decisions when assigning the importance of one factor over another, is used to find the weights of these factors. FUZZY, a computer program developed based on the fuzzy decision-making system (FDMS) is used to generate the activity relationship charts. These charts are used by FZYCRLP, a modified version of CORELAP, to develop the layouts. FELAP, another program based on FDMS is used to evaluate the layouts. The new evaluation method uses the distances and the relationships between departments to score the layout. The scoring system, which ranges from zero to ten (ten is the best possible score), can be used to evaluate and compare ally layout regardless of the number of the departments and their size.
