Workflow for calculating total working days?

[jeff_rivers]

Do you calculate the working days for your projects, or do you work with the folks that do?  What is your/their workflow?  

I know the basic calculation, it isn't hard: Quantity divided by production rate per day = days required; add up all the days for all the quantities.  

Of course, some items of work can happen simultaneous with other items, especially as a large project may be broken into several work areas.  That's where it turns into a giant mind game.  

So what is your workflow?  WHO in your organization calculates working days?  WHEN in the life of the project do they do it?  WHAT unique tools or resources do they use?  

Thanks!  

[Joe-Bouza]

Are we talking Design phase or construction Phase?

Design; we try to guesstimate a drawing list and apply a generalized hours per sheet, taking into account meetings, reports etc...

construction; idk