Ever wonder exactly how much kinetic energy is released by an arrow, based on its initial speed and distance traveled? Let’s find out.
Crossbow Arrow Kinetic Energy Chart:
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You can see that as the arrow travels, its kinetic energy decreases, mostly due to air resistance (drag). For example, an arrow fired at a starting speed of 350 FPS will have a kinetic energy 103.8 ft-lbs, but only 87.5 ft-lbs 50 yards out. Keep in mind that 87.5 ft-lbs is more than the recommended minimum (65 ft-bs) for taking the toughest game, such as Grizzly and Buffalo.
How did we test this?
We shot 400 grain arrows from 22 different crossbows, achieving nine different initial speeds ranging from 200 to 400 FPS in 25 FPS increments as measured by our chronograph. We then used our arrow ballistics calculator to figure out the kinetic energy at
This is as close as it gets to what your arrows will deliver in the field, though keep in mind that our tests were conducted at an indoor range to avoid wind and weather fluctuations which can impact arrow behavior, so actual kinetic energy values in the field can and probably will vary slightly from what we arrived at in our tests.
Why Did We Use 400 Grain Arrows In Our Tests?
Most of the best crossbows on the market are rated using 400-grain arrows. For example, a crossbow rated at 350 FPS was likely tested with a 400 or 425-grain arrow. We choose 400-grain arrows to make sure that our results reflect what most new crossbow buyers will experience with the arrows included in their crossbow package.
What If I Use Heavier Arrows? How Does It Affect My Kinetic Energy?
Your arrow’s kinetic energy depends on its speed. Heavier arrows are slower, reducing their kinetic energy. The key question is: how much does arrow speed drop as weight increases? While we haven’t conducted precise tests yet (we’ll update this when we do), here’s a close estimate assuming only the arrow weight changes, with no adjustments to the crossbow:
- 425 grain: 97.5% of base speed
- 450 grain: 95% of base speed
- 475 grain: 92.3% of base speed
- 500 grain: 90% of base speed
- 525 grain: 87.8% of base speed
- 550 grain: 85.5% of base speed
- 575 grain: 84% of base speed
- 600 grain: 82.5% of base speed
Example:
If your crossbow is rated to shoot 400-grain arrows at 350 FPS, a 500-grain arrow will shoot at ~315 FPS (90% of 350), and a 600-grain arrow at ~290 FPS (82.5% of 350). Again, these are close estimates.
To calculate your kinetic energy, plug the adjusted arrow speed and its weight into our kinetic energy calculator.
How Much Kinetic Energy Do You Need To Hunt Specific Game?
The chart below demonstrates the minimum, as well as recommended, kinetic energy, for hunting different-sized game. We strongly advise that you stick with the “recommended” values to maintain lots of room for error, particularly if you’re new to hunting.
Recommendations based on calculations by Easton Archery.
Observations From The Main Kinetic Energy Chart Above
Here are some interesting things to note, based on the kinetic energy chart at the top of this page:
#1: Kinetic energy drops are fairly predictable. You can assume, roughly, that an arrow’s kinetic energy is reduced by around 3-4% for every 10 yards it travels. So if we have 100 ft-lb of initial energy (at 0 yards), at 10 yards you can expect roughly 97-97 ft-lbs of KE.
This is a good rough rule to remember in case you need to do some quick, on-the-spot kinetic energy calculations in the field. Please keep in mind that this approach will only give you close estimates, and that it becomes less accurate the further out we go (I wouldn’t suggest using it for anything beyond 70 yards, which is far beyond what you’ll be hunting from anyway).
#2: Even a 50 FPS speed difference alters kinetic energy significantly. If you use the chart above to compare kinetic energy between a 350 FPS and a 300 FPS crossbow, you’ll notice that the first one delivers significantly more KE at 50 yards than the second crossbow does at 10 yards! That’s a massive difference in a hunting scenario.
#3: Not all crossbows are suitable for hunting. Notice that our recommendation for elk hunting is 65 ft-lbs of kinetic energy (this is a conservative value; you can get away with less). Notice that at 250 FPS, this value cannot be achieved. Even at 275 FPS, you only get close to it at 10 yards. It’s only from 300 FPS and up that you get enough kinetic energy at all feasible hunting distances (up to 50 yards) to be able to comfortably hunt elk. As such, we recommend that elk hunters stick to 300 FPS or more. For whitetail deer, this requirement is lower—any crossbow 250 FPS and up will be a safe pick. Compare expected FPS across over 120 crossbows and decide which one to buy.
#4: 325 FPS is more than enough for the overwhelming majority of hunters. With a 325 FPS crossbow, your arrow will pack about 70 foot-pounds of energy at the typical ethical hunting distance of 40–50 yards—more than enough to take down even the toughest game in North America. Unless you’re planning to hunt grizzly bears at 70 yards or farther, you’ll never need more than 325 FPS.
Hopefully, you find the above charts and information useful in determining what crossbow to buy and how kinetic energy changes based on arrow weight and speed.
Other related research:
– Arrow drop test results
– How far can you shoot a crossbow?