Question 1

How do you calculate arrow kinetic energy?

Accepted Answer

Kinetic energy (ft·lb) = arrow weight in grains × speed in fps² ÷ 450,240. A 425-grain arrow at 290 fps: 425 × 290² ÷ 450,240 = 79 ft·lb.

Question 2

How much kinetic energy do I need for deer or elk?

Accepted Answer

The commonly cited minimums are 40 ft·lb for whitetail, antelope and mule deer, and 50 ft·lb for elk, black bear and wild boar. They come from Easton's hunting setup material and state hunter-education courses, and they are guidance rather than law.

Question 3

Which matters more, kinetic energy or momentum?

Accepted Answer

For penetration on game, momentum, along with arrow weight and broadhead design. Kinetic energy is a useful minimum; past it, a heavier arrow with more momentum usually penetrates further than a lighter one with the same energy.

Question 4

How much energy does an arrow lose downrange?

Accepted Answer

In this calculator's model, roughly 10 to 16% by 40 yards, depending on arrow weight: heavier arrows keep more. Large vanes or feathers slow an arrow faster than the model assumes.

Question 5

Does a heavier arrow carry more energy?

Accepted Answer

At the bow, about the same: the bow puts a similar amount of energy into arrows across normal hunting weights. A heavier arrow carries more momentum, though, and keeps more of its energy downrange.

Game	Minimum	Your arrow keeps it
Small game / turkey	25 ft·lb	past 100 yd
Whitetail / antelope / mule deer	40 ft·lb	past 100 yd
Elk / black bear / wild boar	50 ft·lb	past 100 yd
Moose / large plains game	65 ft·lb	to 56 yd
Cape buffalo / dangerous game	80 ft·lb	not at the bow

Distance	Speed	Kinetic energy	Momentum
bow	290 fps	79 ft·lb	0.55
10 yd	285 fps	77 ft·lb	0.54
20 yd	280 fps	74 ft·lb	0.53
30 yd	275 fps	71 ft·lb	0.52
40 yd	270 fps	69 ft·lb	0.51
50 yd	265 fps	66 ft·lb	0.50
60 yd	261 fps	64 ft·lb	0.49

Commonly cited minimums

Downrange