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IBO Speed Rating (fps) Manufacturer's IBO/ATA rating (200–400)

Draw Weight (lbs) Actual draw weight at your draw length (20–100)

Draw Length (inches) Your measured draw length (20–35)

Arrow Weight (grains) Total arrow weight with point (200–1200)

String Accessory Penalty (fps) Peep, D-loop, silencers penalty (0–30)

Quick Presets

Arrow Speed —

Kinetic Energy —

Momentum —

Grains per Lb —

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About

Estimating arrow velocity without a chronograph requires precise modeling of energy transfer from bow limbs to the arrow shaft. This calculator uses the IBO (International Bowhunting Organization) rating system as a baseline, then applies correction factors for draw length, draw weight, arrow mass, and string accessory weight. The IBO standard assumes a 30″ draw length, 70lb draw weight, and 350gr arrow. Every deviation from these reference values shifts the predicted speed by empirically derived coefficients. Getting arrow speed wrong has consequences: underestimating velocity leads to incorrect sight tape settings and poor trajectory prediction, while overestimating it causes dangerously low arrow spine matching and potential equipment failure.

The tool also computes kinetic energy (KE) and momentum (p), which determine penetration performance on game animals. Most bowhunting regulatory bodies recommend a minimum of 25ft⋅lbs for whitetail deer and 65ft⋅lbs for elk-class animals. Note: this model approximates real-world performance assuming a well-tuned bow with no significant cam lean, cable guard friction, or limb fatigue. Actual chronograph readings may vary ±5 - 10fps from predicted values.

Formulas

Arrow speed is derived from the bow's IBO rating with correction penalties applied for each deviation from the IBO reference conditions.

v = IBO − 10 × (30 − DL) − AW − 3503 − S + 2 × (DW − 70)

Where v = arrow speed in fps, IBO = manufacturer IBO rating in fps, DL = draw length in inches, AW = total arrow weight in grains, S = string accessory penalty in fps (typically 3 - 5 fps per accessory), DW = draw weight in lbs.

Kinetic energy is computed from the classical mechanics equation:

KE = AW × v²450240

Where KE is in ft⋅lbs, AW in grains, and v in fps. The constant 450240 converts grains and fps² to ft⋅lbs (derived from 7000 gr/lb × 2 × 32.174 ft/s²).

Momentum is calculated as:

p = AW × v225120

Where p is in slug⋅ft/s. The constant 225120 equals 7000 gr/lb × 32.174 ft/s².

Reference Data

Game Animal	Min KE (ft⋅lbs)	Recommended Momentum (slug⋅ft/s)	Min Arrow Weight (gr)	Effective Range (yd)
Small Game (Rabbit)	15	0.25	250	20 - 30
Turkey	25	0.35	350	20 - 35
Whitetail Deer	25	0.40	350	20 - 40
Mule Deer	35	0.45	400	20 - 40
Pronghorn	25	0.40	350	20 - 40
Black Bear	40	0.50	400	20 - 35
Wild Boar	45	0.50	450	15 - 30
Elk / Wapiti	65	0.65	450	20 - 40
Moose	65	0.65	500	15 - 35
Grizzly Bear	65	0.70	500	15 - 30
Cape Buffalo	80	0.85	650	15 - 25
Elephant (Legal Areas)	90	1.00	750	10 - 20

Frequently Asked Questions

IBO-based estimates are typically within ±5-10 fps of actual chronograph readings for well-tuned compound bows. Discrepancies arise from factors the model cannot capture: cam timing, limb tiller balance, cable guard friction, arrow spine flex, nock fit tightness, and ambient temperature. Cold weather (below 40 °F) can reduce limb performance by 2-5 fps. Always verify with a chronograph before hunting season.

Shooting an underweight arrow is equivalent to dry-firing the bow. The excess energy that the arrow cannot absorb transfers back into the limbs, cams, and riser, risking catastrophic failure. The industry-standard minimum is 5 grains per pound of draw weight (e.g., 350 grains at 70 lbs). Many manufacturers void the warranty below this threshold. Some target archers push to 4.5 gr/lb, but this is not recommended for hunting setups.

Kinetic energy measures the total work an arrow can do, but momentum (p = m × v) better predicts penetration through dense tissue, bone, and hide. A heavier, slower arrow retains more momentum upon impact than a lighter, faster arrow with the same kinetic energy. Dr. Ed Ashby's broadhead study found that arrows with momentum above 0.65 slug·ft/s achieved complete pass-throughs on elk-sized game over 90% of the time, regardless of broadhead type.

Each inch of draw length below the IBO reference of 30 inches reduces stored energy in the limbs. The empirical correction is approximately 10 fps per inch. A 28-inch draw archer shooting the same bow loses roughly 20 fps compared to the IBO rating. This is because the power stroke (distance over which the string accelerates the arrow) is shortened, reducing the impulse delivered to the arrow.

Every gram of weight added to the bowstring (peep sights, D-loop, silencers, nocking points) absorbs energy that would otherwise go to the arrow. The general rule is 1-2 fps lost per additional grain of string weight. A typical setup with a peep sight (10-15 gr), D-loop (8-12 gr), and two string silencers (15-25 gr each) totals roughly 8-15 fps of penalty. Bare-string IBO tests have none of these accessories.

This calculator is optimized for compound bows with a known IBO rating. Recurve and longbow performance varies more dramatically due to differences in limb design, brace height, string material, and archer technique. For traditional bows, a rough estimate uses the formula: speed ≈ 150 + (draw weight × 1.1) − (arrow weight − 400) / 5. However, chronograph testing is strongly recommended for traditional setups, as individual variation exceeds ±15 fps.

Yes. Compound bow limbs are made of fiberglass or carbon-fiber composites whose elasticity decreases in cold temperatures. Testing shows a loss of approximately 1-2 fps per 10 °F drop below 70 °F. At 20 °F, expect 5-10 fps lower than summer readings. String materials (Dyneema/BCY-X) are less affected, but lubricant viscosity in cam bearings increases, adding additional friction losses. This calculator does not model temperature effects; add a manual correction if hunting in extreme cold.