How is % Complete Calculated?
% Complete is based on the duration of the tasks in the Gantt chart. For example, a one-day task will have half the weight as a two-day task.
Tasks not yet scheduled, or without a due date, will not affect the % complete calculation. This is because the system cannot appropriately determine the weight of the task in relation to the rest of the project. Moreover, it does not take a task's estimated hours into account in the calculation.
In the screenshot above, the overall % complete is 10% since two out of three tasks in the task group are not scheduled. Even if task B and C are marked as 100% and 90% done, TeamGantt only considers task A as part of the calculation since it is scheduled into the Gantt chart.