Determining software characteristics that will effectively support project planning, execution, monitoring and closure remains to be one of the prevalent challenges software project managers face. Functional size measures were introduced to quantify one of the primary characteristics of software. Although functional size measurement methods have not been without criticisms, they have significant promises for software project management. In this paper, we explore the contributions of functional size measurement to project management. We identified diverse uses of functional size by performing a literature survey and investigating how functional size measurement can be incorporated into project management practices by mapping the uses of functional size to the knowledge areas defined in project management body of knowledge (PMBOK).