Kinetic Energy Calculator
What Is Kinetic Energy in Archery?
Kinetic energy (KE) is the energy an arrow carries due to its motion. The faster and heavier your arrow, the more energy it delivers on impact—critical for penetration and ethical hunting.
Kinetic Energy Formula
The standard formula for calculating arrow KE is:
- Mass = Arrow weight (in grains)
- Velocity = Arrow speed (in feet per second, FPS)
- 450,240 = Conversion factor (grains to pounds, FPS to ft-lbs)
Example Calculation:
- Arrow weight: 400 grains
- Arrow speed: 280 FPS
- KE = (400 × 280²) / 450,240 = 69.7 ft-lbs
(Need a chronograph to measure arrow speed? Check out our top-rated picks here.
Check Out The Advanced Arrow Setup Calculator
Kinetic Energy vs. Momentum: Why Both Matter
| Factor | What It Measures | Why It Matters |
|---|---|---|
| Kinetic Energy (KE) | Force of impact | Determines initial penetration power |
| Momentum (p) | Ability to sustain penetration | Ensures deep pass-through shots |
Momentum Formula
Momentum=mass×velocity1000Momentum=1000mass×velocity
- Higher momentum = Better penetration on tough game (e.g., elk, Cape buffalo).
- Higher KE = More explosive impact, ideal for lighter game (e.g., deer, turkey).
Pro Tip: For large game, prioritize momentum (heavier arrows). For long-range accuracy, prioritize KE (faster, lighter arrows).
Recommended Kinetic Energy for Hunting
| Game Type | Minimum KE (ft-lbs) | Ideal Arrow Setup |
|---|---|---|
| Small Game (rabbits, turkey) | 25+ | Light arrow (300–400 grains), high speed (300+ FPS) |
| Whitetail Deer | 40–65 | Mid-weight arrow (400–450 grains) |
| Elk, Black Bear | 65+ | Heavy arrow (500+ grains) |
| Cape Buffalo, Grizzly | 80+ | Extreme FOC arrows (600+ grains) |
Key Insight:
- Lighter arrows fly flatter but lose momentum quickly.
- Heavier arrows penetrate deeper but drop faster.
How to Increase Kinetic Energy & Momentum
1. Adjust Arrow Weight
- Lighter arrows = Higher speed → More KE
- Heavier arrows = More momentum → Better penetration
2. Increase Draw Weight
- A 70-lb bow generates more KE than a 50-lb bow at the same arrow weight.
3. Optimize Bow Efficiency
- Compound bows transfer energy better than recurves.
- High-quality cams & strings reduce energy loss.
4. Use an Arrow KE Calculator
Online tools (like this one) let you input arrow specs and instantly see KE/momentum values.
Common Bowhunting Mistakes to Avoid
❌ Over-prioritizing speed – A 350 FPS arrow with low weight may lack penetration.
❌ Ignoring FOC (Front-of-Center) – A well-balanced arrow (12–15% FOC) flies straighter.
❌ Using the wrong broadhead – Fixed blades outperform mechanicals on heavy game.
Pro Tip: Test different setups on a ballistic gel target to compare penetration.
FAQs
Q: How does gravity affect arrow KE?
A: Gravity pulls arrows down, reducing speed (and KE) over distance. Always account for drop at longer ranges.
Q: Can a lighter arrow penetrate better?
A: Only if shot at much higher speeds—otherwise, heavy arrows win for deep penetration.
Q: What’s the best arrow for elk hunting?
A: A 500+ grain arrow with 15% FOC and 65+ ft-lbs KE ensures ethical kills.
Q: Do I need a chronograph?
A: Yes—measuring real-world arrow speed is critical for accurate KE calculations.
Final Verdict: Balance KE & Momentum for Success
✔ For deer & medium game: Aim for 40–65 ft-lbs KE with a balanced arrow.
✔ For elk & large game: Prioritize momentum (heavy arrows, 65+ ft-lbs).
✔ For extreme penetration (buffalo): Use 600+ grain arrows with high FOC.
Need gear recommendations? Check out our best hunting arrows