Bowhunting Setup Analyzer
Calculate kinetic energy, momentum, FOC, and recommended arrow spine for your bow setup.
Bow & Arrow Setup
40–80 lbs typical hunting range
24–32 in typical
Measured from nock groove to tip of insert
Found on arrow shaft packaging (6–12 GPI typical)
IBO speed or chronographed speed
Measure where assembled arrow balances on your finger. Leave blank to skip FOC.
Results
358
Total Grains58.0
KE (ft-lbs)0.429
Momentum.300
SpineRecommended Arrow Spine: .300
.300 (stiff)
Frequently Asked Questions
FOC is the percentage of the arrow's total length that falls in front of the midpoint. It indicates how front-heavy the arrow is. Ideal hunting FOC is 11–15% — enough to ensure stable, accurate arrow flight and good penetration. Lower FOC (<7%) causes erratic flight; very high FOC (>19%) can cause fishtailing.
Most bowhunting authorities recommend a minimum of 25 ft-lbs for whitetail deer, though 40+ ft-lbs provides a larger margin. For elk and large game, 42–65 ft-lbs is recommended. More kinetic energy means deeper penetration, especially through heavy bone.
Arrow spine (stiffness) must match your draw weight, draw length, arrow length, and point weight. Underspined arrows (too flexible) fishtail and lose accuracy. Overspined arrows (too stiff) fly erratically. The AMO spine chart is the industry standard — this calculator uses it with draw-length and arrow-length modifiers.
Momentum (grain-fps / 225,400) represents the arrow's ability to maintain velocity through resistance — i.e., penetration. A heavier arrow at the same kinetic energy will have higher momentum and penetrate deeper. This matters most for heavy-boned game like elk, bear, and moose.