Article — Arrow Speed Calculator
Arrow Speed: How Bow and Arrow Setup Determines FPS
Arrow speed is set by four variables: bow IBO rating, draw weight, draw length, and arrow grain weight. Each unit over the IBO baseline (70 lbs, 30 inches, 350 grains) shifts the speed by a predictable amount. Most modern compound bows produce 270–340 fps in real-world setups.
Knowing arrow speed matters for two reasons. First, it sets the arrow's trajectory — faster arrows drop less and need fewer pin holds at different distances. Second, it determines kinetic energy and momentum, which control penetration. A 290 fps arrow at 400 grains carries more terminal energy than a 320 fps arrow at 300 grains, even though it's slower. This article covers how to estimate your real speed, why it differs from the marketing number, and what speed actually means for the hunt.
What is arrow speed?
Arrow speed is the velocity of the arrow at launch, measured in feet per second (fps) in the US and metres per second (m/s) elsewhere. It is the single most useful performance metric for a bow setup, because trajectory, energy, and time-to-target all flow from speed.
The speed you actually get from your bow depends on the geometry of the cam draw cycle, the energy stored in the limbs at full draw, and the efficiency of the energy transfer to the arrow. Lighter arrows leave the bow faster because there is less mass to accelerate, but they also carry less momentum and slow down more in flight.
The fastest production compound bows hit 370+ fps under IBO conditions. The current world record arrow speed from a compound bow is about 480 fps, set with a custom rig and 200-grain arrow — not legal for hunting in most states.
IBO speed standard
The International Bowhunting Organization (IBO) set the speed-testing standard now used by every major bow manufacturer. To qualify as an "IBO speed", a bow must be tested with exactly 70 lbs of draw weight, 30 inches of draw length, and a 350-grain arrow.
The IBO number is the marketing figure printed on bow tags and websites. It's a useful comparison between bows but rarely matches what you'll see on a chronograph. The reasons are simple: most hunters draw less than 30 inches, pull less than 70 lbs, and shoot arrows heavier than 350 grains. Each deviation knocks fps off the IBO baseline.
- IBO conditions = 70 lbs, 30 inch draw, 350 gr arrow, no accessories
- ATA speed = similar standard but slightly different: 60 lbs, 30 in, 9 gr/lb arrow (270 gr)
- AMO speed = older standard: 60 lbs, 30 in, 540 gr arrow (much slower numbers)
- Marketing speed = always IBO unless stated otherwise
The arrow speed adjustment formula
The standard adjustment rules let you predict your actual speed from the IBO number. They are approximations — every bow's cam profile is slightly different — but accurate to within about 5–10 fps for modern compound bows.
+1 inch draw +10 fps+1 lb draw weight +2 fps+10 grains arrow -2 fpsString accessories -1 to -3 fps per 10 grThe math: a 65-lb bow at 28-inch draw with a 400-grain arrow starts from an IBO of 330 fps and ends up at about 330 - 10 - 20 - 10 = 290 fps. Plus or minus 5 fps depending on the specific bow.
Arrow kinetic energy and momentum
Speed alone doesn't kill — kinetic energy and momentum do. The two are calculated differently and emphasise different physics.
Kinetic energy uses the formula KE = (grains × fps²) / 450,240, with the result in foot-pounds. KE scales with the square of speed, so faster arrows have disproportionately more energy on paper. A 290 fps arrow at 400 gr has 74.7 ft·lbs of KE.
Momentum uses p = (grains × fps) / 225,218, with the result in slug-fps (or lb·s/ft). Momentum scales linearly with speed and mass. Many traditional and trad-friendly hunters favour momentum as the better penetration predictor.
Arrow speed thresholds for hunting
Most state agencies and bowhunting organisations publish KE thresholds for different game classes. They vary, but the consensus values are:
- Small game (rabbits, turkey) = 25 ft·lbs minimum
- Whitetail deer = 40 ft·lbs minimum, 50+ preferred
- Elk, mule deer = 55 ft·lbs minimum, 65+ preferred
- Moose, brown bear = 65 ft·lbs minimum, 75+ preferred
- Cape buffalo = 80 ft·lbs minimum, 90+ preferred
Speed itself doesn't make a hunt ethical — shot placement, arrow flight, and broadhead design carry equal weight. But adequate energy is non-negotiable.
Variables that affect arrow speed
Beyond the four headline inputs, several less-visible factors change real-world arrow speed. Bow tuners track all of them.
If your chronograph reads 8 fps slower than the calculator predicts, check accessories first. A peep sight, D-loop, kisser button, and string silencers can collectively add 20+ grains to the string, costing 2–6 fps.
- String accessories = peep, loop, kisser, silencer all slow the string
- Cam style = aggressive single cams beat smooth dual cams by 10–20 fps
- Brace height = shorter brace = more power stroke = more speed (but harder to shoot)
- Bow age = limbs lose 1–3% per year of efficiency
- Arrow spine = under-spined arrows lose energy to flexing
- Release type = mechanical release beats finger release by 3–5 fps
Common arrow speed mistakes
Setup mistakes that cost speed are remarkably consistent.
An arrow that's too weak for your draw weight bends too much during the shot, wasting energy as flex rather than forward motion. Always match arrow spine to draw weight — consult a manufacturer chart.
- Comparing IBO to chronograph — they're never equal; expect 10–20 fps difference.
- Ignoring accessory weight — every gram on the string costs speed.
- Pulling too much draw weight — past max, technique degrades and speed drops.
- Over-light arrows — below 5 grains per pound is unsafe and damages the bow.
- Wrong draw length — too long or short kills speed and consistency.
Tuning vs raw arrow speed
A well-tuned 290 fps bow with consistent groups beats a poorly-tuned 320 fps bow that scatters arrows across the target. Speed is a starting point, not a destination. Spend time on paper tuning, broadhead flight, and shot execution before chasing the last 5 fps.
Modern compound bows in the 290–310 fps range with arrows in the 400–450 grain range hit the sweet spot for hunting whitetail and similar game. Slightly slower than the marketing number, but more forgiving in real-world conditions.