For over a decade, leaders in the Department of Defense (DoD) have asked “What is the value of simulation based training?� or “Why should I spend one more dollar on simulation?�. The easiest answer may be the qualitative benefits of simulation that pertain to areas like safety, availability, flexibility in scenarios, and protection of operational plans. But leaders want quantitative measures such as Return on Investment (ROI), and ROI for simulation has two major facets: cost and benefit (often called results). The authors’ research has focused on answering the DoD questions with cost avoidance computations because cost avoidance is a key component of ROI calculations, and with proficiency improvement evaluations to determine if use of simulation has a quantitative benefit. The authors will present their methods of calculating cost avoidance over the last four years for many simulation-based training systems managed by the United States Marine Corps Program Manager for Training Systems (PM-TRASYS). The research has shown cost avoidance of over $2B across the PM-TRASYS systems analyzed, but the authors are also developing methods to refine these measures of cost avoidance. These more realistic measures are linked to live training requirements allowed to be conducted in simulation and/or to proficiency increases due to use of simulation. These same cost avoidance methods are now being applied to large scale exercises to show the value of using a mix of live-virtual-constructive systems in these scenarios. This paper will also discuss the management data that is gathered and depicted as part of the cost avoidance studies. This data captures use statistics by system and site, and includes data such as the number of Marines trained and munitions used. As will be shown in the paper, this study provides quantitative measures of simulation cost avoidance and results.