Here is a Column Capacity CALCULATOR ... http://courses.cit.cornell.edu/arch264/calculators/example7.1/index.html
Totally COOL! ... note the disclaimers.
Me thinketh that it is for CENTRIC loading ... in fact, IT IS ... here's a quick check.
If you put in a length of, say, 0.1 ft, the C_P should be essentially 1.00. Further, for Normal load duration, not hot, not wet, etc. ... we should get a column capacity of ...
Let's consider a 6 x 6 `Post and Timber' column of dims 5.5 by 5.5 ...
A = 5.5 x 5.5 = 30.25 sq. in.
Trying DF-L No. 2 ... Fc = 700 psi
All the C's go to unity
So, Fc' = 700 psi times 1's ... = 700 psi.
P_allowable = Fc' A = Fc A ...
So, P_allow = 700 psi (30.25 sq. in.) = 21,175 lb.
Behold, that's what the `calculator' gives us.
Load is indeed assumed to be dead center.
If we allow the load to drift off center ... the capacity will be LESS!