Archery Draw Weight & Arrow Speed
Estimate arrow speed, kinetic energy, and momentum from bow draw weight, draw length, arrow weight, and bow efficiency.
Results
What is it?
Arrow speed is the most influential factor in trajectory and penetration. This calculator uses the work-energy theorem: the energy stored in the bow limbs (draw weight � draw length � efficiency) is converted into arrow kinetic energy. From speed, kinetic energy and momentum are derived � two key metrics for assessing hunting suitability.
How to use
Set your bow's peak draw weight, your draw length, the total finished arrow weight (shaft + insert + point + nock + fletching in grains), and your bow's efficiency percentage. Compound bows are typically 80�85% efficient. The results are ballpark estimates � a chronograph gives exact speed.
Example scenario
A 70-lb compound bow at 29-inch draw, 82% efficiency, launching a 400-grain arrow: estimated speed � 272 fps, KE � 65.7 ft-lbf, momentum � 0.483 slug-fps. Deer typically require 40+ ft-lbf; elk require 65+ ft-lbf � this setup is right on the elk minimum.
Pro tip
Momentum (not kinetic energy) better predicts penetration depth on heavy game because heavier arrows retain energy better through hide and bone. For deer, a minimum of 0.40 slug-fps momentum is recommended. For elk or bear, aim for 0.50+. Never sacrifice arrow spine integrity chasing maximum speed.