questions about 2x4 vs. 2x6 framing
I was browsing through the Building in Mixed Climates book and noticed the author(s) recommended to use 2x6's on 24" centers. He said there is the same board footage, but you use 30% less material/sticks.
How would one go about estimating how much wood is in the walls of a structure? So I would know that a 40'x40' build using 2x4's will need this many sticks and a 40'x40' building using 2x6's will need such and such.
Is there a framing book I could read that would explain cost/material estimation for the framing package of a basic home/structure?
One reason I want to know how to do this is so that I'll know how to do it. Sure, a computer program can crank it out, but I would like to know how to it by hand or using one of those builder's calculators if it would help.
Any other tips?