too many variables....
some stud frames are 2x6 and might even use 16" centers.
I've also seen 2x4 on 24" centers....
and some timberframes use 8x8's on 8' centers, others I've seen(like our old barn) have 10x10 posts on 20' centers......
However, If you have a timberframe book, say ted benson's first book, there is a more or less standard timberframe plan in there. you could pull out the board footage from that frame and call it ballpark.... Then if you take a 2x4 on 16" center or a 2x6 on 24" center stickframe and pull the board footage for the same size footprint as the benson frame(you would be wise to call up a truss company and get ahold of the current center spacing and design for the gang nail trusses) ... again that would only be a ballpark figure..
