What is the best way to estimate a project? Project estimating should be done in a piecemeal fashion as the project is being implemented. The best way to determine the cost estimate is to glean information from historical projects - identify similar tasks, activities, resources and base project cost estimates on these projects. Estimating a project is best done by requesting separate estimates from all team members for their tasks. Estimating a project should be done by the customer when creating a project budget