Component-based software development is one of the proficient models of constructing eminent-quality software products. Reusability is the basic concept behind the component-based software. Reusability suggests re-use of existing software artifacts rather than developing them from the beginning. Components interact to share services and information in component-based software environment. In this paper we have focused on the interaction characteristics of the components. We define a metric called Interaction-metric as a factor of measurement of actual execution time of component-based software. We introduce the role of Interaction-metrics of individual components to estimate the execution-time of the component-based software. Interaction-metric are easy to compute, and are informative to analyze the performance of the components as well as the component-based software.