Currently, the determination of appropriate submarine acquisition and future growth margins is based on previous successful designs. For the most part, this has ensured that recent submarine classes have delivered with the required future growth capability. However, this method does not optimize margin amounts. This paper presents an alternate method of determining margin amounts through the use of a stochastic simulation of the entire life of a submarine: from detail design and construction to delivery, to short availabilities, to overhauls, and finally to decommissioning. By modeling acquisition margin usage and known and unknown weight and KG growth as probability distributions (based on actual submarine data), the simulation can provide a probability distribution and certainty values for remaining margin at any point in the submarine's life. Developing acceptable levels of risk for margins for the latter part of the submarine's life will allow the weight engineer to go back and calculate initial acquisition and future growth margins that will be close to optimal for those risk levels. This paper addresses the proposed process, the simulation tool, and some preliminary results, but does not present actual final margin findings or recommendations.