Many U.S. government agencies and their contractors have subscribed to using the prescriptive metric of technology readiness level (TRL) as a measure of maturity of an individual technology, with a view toward operational use in a system context. A comprehensive set of concerns becomes relevant when this metric is abstracted from an individual technology to a system context, which may involve interplay among multiple technologies that are integrated through a system development life cycle. This paper proposes a system-focused approach for managing system development and making effective and efficient decisions during this life cycle. A system readiness level (SRL) index that incorporates both the current TRL scale and the concept of an integration readiness level is presented with methods for determining current and future readiness of a system. Using techniques in evolutionary algorithms, the SRL index is optimized based on resource allocation to provide a decision support approach that enhances managerial capabilities in the system's development life cycle. The optimization model for the SRL is then executed with a case example and resource constraints of 75%, 60%, 45%, 30%, and 15% to demonstrate how it can be used to make strategic planning decisions in the system's development life cycle.