Do you know a task management app able to calculate total duration?
I dont know an app, but Google Sheets can work for this: Put tasks/subtasks down left side. Put days in schedule in column titles. Put in time estimates on days in schedule. Add up time estimates for each day. This way you can see just how realistically you can do all of the work youre hoping to do. Heres a little screenshot of it in action: And heres a link to a spreadsheet I used for a project. Make a copy and play around to see if it will meet your needs.