You’ll need the following accurate information to apply to a simple mathematical formula to arrive at the Kenetic Energy Level for the arrows you have.
Notice this is for the arrow, (not the bow) as it will
change with different arrow brands/weights.
1. Take the completed arrow you intend to use and weigh it
on a scale to obtain it’s total grain weight.
2. Shoot it through a chronograph from your bow at the
draw weight (poundage) you intend to hunt with to obtain
the velocity in FPS.
3. Now for the math part.
Velocity X Velocity X Total Arrow Weight Divided by
450,240. That resulting number equals the “Kenetic
Energy”, or “Foot Pounds”.
This information comes from a past article in Peterson’s Bowhunting Magazine:
Kenetic Energy Minimums
30 – 35+ Foot Pounds Antelope to Deer
40 – 45+ Foot Pounds Midwestern Whitetail Deer
50 – 55+ Foot Pounds Elk to Moose
Just remember to have accurate numbers when it comes to arrow weight and FPS when doing this formula. 
