A decision tool utilizing the magnitudes of system parameters and an associated set of weighting factors has been developed to compare alternative design concepts for new systems. The weighting factors are computed from data describing the system requirements, and they are not assigned a priori. The magnitudes for the system parameters and the weighting factors are combined in a new, unique manner, not by direct multiplication. Both of these operations can be implemented on a computer; consequently, alternative design concepts can be compared rapidly in the presence of and in response to changing system requirements. This decision tool is primarily for use during the preliminary design phase of a system.