An estimation system for deriving multi-dimensional project plans for implementing packaged software applications with self-calibration and refinement of project estimation models, the system includes: a view layer configured to act as a user interface for user inputs and system outputs; a model and control layer configured to implement rules based on a series of estimation and implementation models, and to perform self-calibration and refinement of project estimation models for multi-dimensional project plans; an estimation knowledge base layer configured to hold and derive the series of estimation and implementation models; and wherein the system for self-calibration and refinement of project estimation models for multi-dimensional project plans for implementing packaged software applications is carried out over networks comprising: the Internet, intranets, local area networks (LAN), and wireless local area networks (WLAN).