I thought I could figure it out but none of my old trad-books help me in figuring out arrows made of the new materials. I am trying to get a handle on figuring it all out so when I read the specs I can at least say to myself "these are in or out of the ballpark" for the bows I shoot.
Thanks!
God bless,Mudd

I don't know of any source material that covers all that is carbon.  Your best bet would be to visit the websites of each individual arrow maker, like Easton, Beman, Goldtip, or whomever and read their specs pertaining to the arrow in question.  Most sites will give you a round about poundage for each of there sizes, and will also give you Grains per inch, and sometimes the deflection.  They seem to change every year as well with the addition of new arrows, and sizes.  Tim

If your talking Aluminium it used to be the shaft Diameter in 100ths and the wall thickness in 1000ths of an inch. So 1918 has diameter is .19 inchs in diameter and the wall thickness is .018 thick.

Of course this doesn't tell you much for what weight its good for. So Easton and other arrow makers have made general charts to give you an idea or get you close to the right spine. Newer stuff like carbons and some aluminiums are going to a weight range marking like 55-65 or something like that.  
The problem with that is they are assuming all the bows are center shot (modern compounds) so they don't need to worry about spine as much. Bad news for us Tradition bow shooters. It means more trial and error for us.

Unless of course someone has made a chart.Even then it seems to be less acurate to me.

The first two numbers are in 64ths.