I am trying to figure out what size carbon arrows to use with my new bow, I like the speed of a lighter arrow but also like the kinetic energy increase of a heavier arrow, I also realize you lose alot more speed then kinetic energy you gain going heavier.
I' d like to shoot as light a arrow as I can and still keep about 50-55#' s of kinetic energy and I want that 50-55#' s of kinetic energy at 30 yards.

I have a formula for figuring out kinetic energy given arrow weight & velocity.
KE=(total weight of arrow/450240)x(velocityxvelocity)

Finally to my question ........... at what distance using the above formula will I have this amount of Kinetic energy on impact of my target.
I am using this bow strictly for hunting and 30yards is about the max I' d shoot for whitetail and I want make sure I still have at least 50#' s ok kinetic energy at 30 yards.
So at what distance will formula I have reflect the kinetic energy? 10yard? 20 yards? 30 yards?
Greatly appreciated