Arrow Speed Calculator
Instantly estimate arrow speed, kinetic energy, and momentum. Use presets or calibrate using your chronograph.
Input Parameters
Preset Configurations
Calculation Results
Arrow Speed Formula:
v = IBO + 10*(DL - 30) - (SW / 3) - max(0, (AW - 5*DW) / 3)
Where:
IBO = Manufacturer IBO rating (ft/s)
DL = Draw Length (inches)
SW = String Weight (grains)
AW = Arrow Weight (grains)
DW = Draw Weight (lbs)
Kinetic Energy Formula:
KE (ft-lbs) = (AW * v²) / 450436
Momentum Formula:
Momentum (slug·ft/s) = (AW * v) / 225218
How Arrow Speed is Calculated
Our arrow speed calculator uses the widely accepted industry formula that accounts for the key factors affecting arrow velocity. The calculation starts with the manufacturer's IBO (International Bowhunting Organization) rating, which is measured under standard conditions: 30-inch draw length, 70-pound draw weight, and a 350-grain arrow.
The formula then adjusts this baseline speed based on your actual setup:
- Draw Length: Each inch over 30" adds approximately 10 fps, while each inch under subtracts 10 fps.
- Draw Weight: The relationship between arrow weight and draw weight is critical. If your arrow weighs more than 5 grains per pound of draw weight, you'll lose approximately 1 fps for every 3 grains over this threshold.
- Accessory Weight: Additional weight on your string (peep sight, nock loop, etc.) reduces speed by approximately 1 fps for every 3 grains added.
This calculation provides a reliable estimate of your arrow's initial velocity, which is essential for determining kinetic energy, momentum, and trajectory.
Why Calibrate with a Chronograph
While our calculator provides accurate estimates based on industry standards, every bow setup has unique characteristics that can affect performance. Calibrating with a chronograph ensures your calculations match your specific equipment.
Follow these steps to calibrate your bow setup:
- Set up your chronograph in a safe location with proper backstops.
- Shoot several arrows through the chronograph and record the average speed.
- Enter your measured arrow speed and arrow weight into the calibration tool.
- The calculator will determine your effective IBO rating for future calculations.
- Use this calibrated IBO for more accurate predictions with different arrow setups.
This calibration process accounts for factors like bow efficiency, string material, cam design, and other variables that aren't captured in the standard formula.
Recommended KE & Momentum by Game Type
| Game Type | Minimum KE (ft-lbs) | Recommended KE (ft-lbs) | Minimum Momentum |
|---|---|---|---|
| Small Game (rabbits, squirrels) | 15-20 | 25+ | 0.35-0.40 |
| Turkeys | 25-30 | 35+ | 0.40-0.45 |
| Whitetail Deer | 40-45 | 50+ | 0.50-0.55 |
| Elk, Black Bear | 55-60 | 65+ | 0.60-0.65 |
| Large Game (moose, grizzly) | 70-75 | 80+ | 0.70+ |
These values are general guidelines. Shot placement, broadhead design, and arrow construction also significantly impact hunting effectiveness.
Frequently Asked Questions
IBO speed is a standardized measurement defined by the International Bowhunting Organization. It's measured with a bow set at 70 pounds draw weight, 30 inches draw length, and shooting a 350-grain arrow. This provides a consistent baseline for comparing different bows.
Heavier arrows travel slower but carry more kinetic energy and momentum. While speed decreases linearly with added weight, kinetic energy follows a squared relationship with velocity, meaning small changes in speed have significant impacts on energy.
Both are important, but kinetic energy is generally more critical for ethical hunting. Higher KE results in better penetration and more effective tissue damage. However, extremely heavy arrows with very low speed can make accurate shooting at distance more challenging.
Our calculator uses industry-standard formulas that provide estimates within 2-5% of actual chronograph readings for most modern compound bows. For the most accurate results, we recommend calibrating with your own chronograph measurements.
Yes, both factors can influence arrow speed. Colder temperatures can reduce bow efficiency slightly, while higher altitudes with thinner air can result in slightly higher speeds due to reduced air resistance. These effects are typically minor (1-3% variation).
Consider your primary use: target shooting typically benefits from lighter arrows for flatter trajectories, while hunting often favors heavier arrows for better penetration. A good starting point is 5-6 grains per pound of draw weight for hunting, and 4-5 grains per pound for target shooting.