Program Management Office (PMO)
Accurately estimating a project's effort, duration, and costs is one of the most challenging tasks for the Project Manager. At the project start, the Project Manager usually develops macro level estimates. As the project progresses, the Work Breakdown Structure (WBS) is refined. A macro level estimate is used for preliminary planning, creating a global view, and determining project feasibility.
I’ve seen people use a flat overhead rate (anywhere between 10-25% depending on what the project sponsor will tolerate) or trying to add PM tasks to the project plan to build in hours (meetings(client and team), status reports, issue management, and other activities).
My off the cuff answer is 20 percent of total effort will be related to managing the project and not doing the work. This varies widely depending on skills of the team, definition of the work to be done, and effective change management system
7 Signs of a Bad Project Estimate - And How You Can Fix It
View more presentations from Officework Software & Professional Services.