Threaded hanger rod is non-graded rod that for purposes of discussion should be considered SAE grade 2 (although it is probably less). When figuring out tensile on any threaded rod, use the numbers for a bolt of the same diameter.
Note that in almost every case, UNF rods are stronger than UNC threads, as it is the minimum cross section that fails, and seldom the threads. UNF threads leave more cross section after threading.
For rule of thumb, I use 120K psi multiplied by the surface area for grade 8 and 80K for grade 5. These de-rated values allow for the thread form, and give reasonable results. For Grade 2, most manufacturers don't give good quality control in grade 2 fasteners, I use 30K instead of 60K. Grade 2 might as well be ungraded.
On a side note. Most metric fasteners are Grade 7 or better. (7 is sort of an orphan designation) I use 100K times the surface area for all metric fasteners, regardless of declared grade. (unless it is chinesuim, then I use 30K again)
It is silly that we are all still using lbs-force instead of Newtons. I trained in Newtons, but just feel more comfortable describing thing in the
now-defunct units lbs-force.