Growing complexity is one of the main reasons behind failure of many projects. Project management academi-cians have conceived a few complexity characterization models but a comprehensive complexity measurement model encompassing factors of important project constraints i.e. scope, time and cost is still missing. In this research, a model has been developed to compute PECI (Project Execution Complexity Index) for various categories of projects considering varying levels of complexity, i.e. PECI(R) for R&D/Technology projects, PECI(I) for Infrastructure devel-opment projects and PECI(O) for Other projects. A complexity scale starting from 0 = least complex to 10=highly complex has also been proposed in order to rank and compare the projects. This ranking will help the decision makers to decide which projects to include in their portfolio and which projects to give priority while assigning resources more efficiently. Moreover, project managers will be able to manage their projects better, by first comparing them in order of complexity, followed by tweaking the factors which contribute towards enhancing their complexities.