Arrow Speed Calculator
Calculate real arrow velocity based on your bow setup
Compute actual arrow speed, momentum, and kinetic energy from IBO rating
Actual arrow speed
Plus its momentum and kinetic energy
What is IBO Speed and Why Does It Matter?
Ever looked at a bow's specs and seen something like "IBO 320 fps"? That number sounds impressive, but here's the thing — it's measured under very specific conditions that probably don't match your setup. Let me explain.
🏹 IBO stands for International Bowhunting Organization — the group that standardized how bow speed is measured.
When manufacturers test a bow for its IBO rating, they use these exact parameters:
- 1Draw length: 30 inches
- 2Draw weight: 70 pounds
- 3Arrow weight: 350 grains (5 grains per pound of draw weight)
But let's be real — most archers don't shoot with exactly these settings. Maybe you have a 28-inch draw length, or you prefer heavier arrows for better penetration. That's where this calculator comes in handy. It takes your actual bow setup and calculates what your real arrow speed will be.
The Physics Behind Arrow Speed
The calculation isn't just guesswork — it's based on well-established relationships between bow mechanics and arrow performance. Here's how each factor affects your arrow speed:
📏 Draw Length
For every inch shorter than 30", you lose about 10 fps. For every inch longer, you gain 10 fps. Makes sense — a longer draw stores more energy.
⚖️ Arrow Weight
Heavier arrows beyond the minimum (5 grains per lb of draw weight) will slow down. Every extra 3 grains costs you about 1 fps.
🔧 String Accessories
Peep sights, silencers, D-loops — they add weight to your string. Every 3 grains of string weight costs about 1 fps.
💪 Draw Weight
More draw weight = more energy transferred to the arrow. The minimum arrow weight scales with draw weight (5 grains per pound).
The Master Formula
v = IBO + (L − 30) × 10 − W/3 + min(0, −(A − 5D)/3)
Where: v = actual speed, IBO = rated speed, L = draw length (in), W = string weight (gr), A = arrow weight (gr), D = draw weight (lbs)
Speed alone doesn't tell the whole story. For hunting, kinetic energy (measured in foot-pounds) determines penetration power. Generally, you need at least 25 ft-lbs for small game, 40-50 ft-lbs for deer-sized animals, and 65+ ft-lbs for elk or larger game.
Step-by-Step Calculation Example
Let's walk through a real example. Say you've got a bow rated at IBO 300, and you want to see how fast your arrows will actually fly with your personal setup.
Enter your bow's IBO rating
We'll use 300 fps for this example.
Input your draw length
Let's say yours is 32 inches — that's 2 inches longer than the IBO standard.
Enter your draw weight and arrow weight
Peak draw weight: 70 lbs, Arrow weight: 400 grains
Add any string accessories
With a peep sight and silencers, let's add 5 grains of string weight.
Get your results!
v = 300 + (32-30)×10 − 5/3 + min(0, −(400−350)/3)
v = 300 + 20 − 1.67 − 16.67
v ≈ 301.67 fps
The longer draw adds speed, but the heavier arrow and string accessories bring it back down slightly.
When You'll Find This Calculator Useful
Setting Up a New Bow
Bought a new bow? Predict how your arrows will perform before you even hit the range.
Hunting Preparation
Make sure your setup has enough kinetic energy for ethical, clean shots on your target game.
Arrow Selection
Experimenting with different arrow weights? See how each option affects speed and energy.
Target Shooting
Dial in your sight pins more accurately by knowing your true arrow velocity.
Comparing Bows
Shopping for a new bow? Compare how different IBO ratings translate to real-world performance with your setup.
Tuning Your Setup
Fine-tune the balance between arrow speed, weight, and accessories for your perfect shot.
Pro Tips from Experienced Archers
Speed isn't everything
A 400-grain arrow at 280 fps often outperforms a 300-grain arrow at 320 fps for hunting. Heavier arrows carry more momentum for better penetration through bone and tissue.
The 5 grains per pound rule
Never shoot arrows lighter than 5 grains per pound of draw weight. Lighter arrows can damage your bow and void warranties. At 70 lbs, that's a minimum of 350 grains.
Validate with a chronograph
This calculator gives great estimates, but nothing beats real-world testing. Consider investing in a chronograph or visit a pro shop that has one.
String weight adds up quickly
Peep sight (~10 gr), D-loop (~15 gr), silencers (~10 gr) — it's easy to have 30+ grains on your string, costing you 10 fps. Keep your string lean if speed matters.
Kinetic Energy Requirements for Hunting
Knowing your kinetic energy helps ensure ethical, effective shots. Here's a general guide:
| Kinetic Energy | Suitable For | Examples |
|---|---|---|
| Under 25 ft-lbs | Target practice only | Foam targets, competition |
| 25-40 ft-lbs | Small game | Rabbits, turkeys |
| 40-50 ft-lbs | Medium game | Whitetail deer, pronghorn |
| 50-65 ft-lbs | Medium-large game | Mule deer, black bear, wild boar |
| 65+ ft-lbs | Large game | Elk, moose, grizzly bear |
Frequently Asked Questions
How can I measure arrow speed without a chronograph?
There's a clever field method that works pretty well:
- Shoot a group at 20 yards using your 20-yard pin
- Mark the center of that group
- Move back to 40 yards but keep using the 20-yard pin
- Shoot another group and measure how far below it hits
💡 The drop distance correlates to speed: 15.5" drop ≈ 300 fps, 20.6" ≈ 260 fps, 28.7" ≈ 220 fps
What's the fastest an arrow can travel?
It depends on your bow type:
- Recurve bows: Up to 225 fps (about 150 mph)
- Compound bows: Up to 350+ fps (about 240 mph)
- Longbows: Generally slower due to heavier arrows
Modern speed bows with light arrows can push past 360 fps, but most hunters prefer the 280-320 fps range for better accuracy and arrow durability.
Does weather affect arrow speed?
Yes, but probably less than you'd think. Rain and moisture can slightly slow arrows due to increased drag and water weight on the fletching. Temperature affects bow limb performance — cold weather can reduce speed by 3-5 fps as the limbs become stiffer.
🌧️ Wind is the bigger factor — it won't change your arrow's initial speed, but it dramatically affects accuracy and flight path.
Should I prioritize speed or arrow weight for hunting?
This is the eternal debate! Here's how to think about it:
- Heavier arrows (400+ gr): Better penetration, quieter shot, more forgiving on form errors
- Lighter arrows (300-350 gr): Flatter trajectory, less drop at distance, faster follow-up
Most experienced hunters lean toward heavier arrows. The extra penetration and momentum matters more than raw speed, especially on larger game. A well-placed heavy arrow at 280 fps beats a light arrow at 330 fps every time.
How accurate is this calculator?
The formula is based on the industry-standard IBO adjustment rules and is typically accurate within 3-5 fps of chronograph readings for well-maintained bows. Factors that might cause variation include:
- Bowstring age and condition
- Limb efficiency differences between bow models
- Arrow spine matching and arrow rest type
💡 Use this calculator for planning and comparison. For precise data, validate with a chronograph before relying on the numbers for sight tapes or ballistic calculations.
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