Tom

[tjbottini]

What is the best way to determine how much lumber is needed to frame a wall/room including closets?

[HayZee518]

figure out the square footage of a wall for sheetrock coverage. for studs, take your wall length and divide by 16 inches. add two more studs for openings [doors etc] add another two studs for above the door where the lintel and sleepers will go. a plate will go down on the floor and another will go at the ceiling.

[pushkins]

wall length in inches divided by 16 PLUS 1 = number of studs required for any given length of wall. Top and bottom plates will be length divided by length of stud used (12' wall = 1 x 12' stud or 1.4 x 8' studs etc...). More often than not door openings do not start on 16" centers so I always add in 4 more studs (2x kings and 2x jacks) for every door opening.
I also always add in 3 extra studs for the header and small studs above every door.
If your building walls that intersect with each other then add in 1 more stud for every corner as a drywall nailer.

[Drywall DIY Guy]

Lumber

I am not a carpenter by trade, but for a single room, I simply start measuring and making a list. Then add a few extra boards. You have to account for additional framing needed around doors and windows. Go to the website How To Frame A Window Rough Opening - How To Build A Window Rough Opening for more info.

So the total amt of framing depends on how many windows you will have. And if the windows are wider, they may need special headers. Your local lumber store can advise on this.