Arrow Speed Calculator — IBO Speed Adjustment & KE

Estimate your actual arrow speed from your bow's IBO rating, draw length, draw weight, and arrow weight. Includes kinetic energy for bowhunting.

July 11, 2026

Bow's IBO Rated Speed (fps)

Your Draw Length (in)

Your Draw Weight (lb)

Total Arrow Weight (grains)

String Accessory Weight (grains, optional)

Peep sight, string silencers, kisser button — weight added to the bowstring itself, not the arrow.

Estimated Arrow Speed

250.0 fps

Kinetic Energy

58.30 ft-lbs

Draw length adjustment-20.0 fps

Draw weight adjustment-20.0 fps

Arrow weight adjustment (baseline 300 gr)-40.0 fps

String accessory adjustment+0.0 fps

For reference only — this is a rule-of-thumb estimate, not a chronograph reading. Actual arrow speed varies by bow efficiency, cam design, string material, and release technique. Chronograph your own setup for an exact number, especially before relying on kinetic energy for a hunting ethics or state game-department minimum.

Estimated Speed = IBO Speed + (Draw Length − 30) × 10 + (Draw Weight − 70) × 2 − (Arrow Weight − 5 × Draw Weight) ÷ 3 − (Accessory Weight ÷ 3). Kinetic Energy = (Arrow Weight × Speed²) ÷ 450,240. The IBO (International Bowhunting Organization) baseline test standard is 70 lb draw weight, 30 in draw length, and a 350-grain arrow (5 grains per pound of draw weight).

90% found this helpful

Reference Values

Last verified: Jul 10, 2026

Category	Range	What It Means	Status
IBO Standard Baseline ★	70 lb draw weight / 30 in draw length / 350 gr arrow	The International Bowhunting Organization's rated-speed test standard. A bow's advertised "IBO speed" is measured at this exact setup — 5 grains of arrow weight per pound of draw weight (70 × 5 = 350 gr) — with no accessories on the string.	★ Best
Draw Length Adjustment	±10 fps per inch of deviation from 30 in	Every inch of draw length below the 30 in baseline costs about 10 fps; every inch above adds about 10 fps. This is the single biggest speed factor for most archers since draw length is fixed by the shooter's body, not a tuning choice.	Good
Draw Weight Adjustment	±2 fps per lb of deviation from 70 lb	Every pound of draw weight below 70 lb costs about 2 fps; every pound above adds about 2 fps. Draws less than the IBO baseline (very common — many hunters shoot 60-65 lb) meaningfully reduce speed from the advertised number.	Good
Arrow Weight Adjustment	∓1 fps per 3 grains of deviation from 5 gr/lb of draw weight	The baseline arrow weight scales with the shooter's actual draw weight (5 grains per pound). Every 3 grains heavier than that baseline costs about 1 fps; every 3 grains lighter gains about 1 fps. Heavier arrows trade speed for kinetic energy and quieter, more forgiving flight.	Good
String Accessory Weight Adjustment	−1 fps per 3 grains added to the string	Nocks, peep sights, string silencers, and kisser buttons added to the bowstring (not the arrow itself) slow the string's return speed. Every 3 grains added costs about 1 fps — this is always a subtraction since it's mass added on top of the baseline, not a deviation that can go either way.	Okay
Kinetic Energy Formula	KE (ft-lbs) = (arrow weight in grains × velocity in fps²) ÷ 450,240	Standard archery kinetic-energy formula used industry-wide to rate arrow momentum for hunting ethics and state game-department minimums. 450,240 is the constant that converts grains and fps into foot-pounds.	Good

Source: IBO (International Bowhunting Organization) test-standard speed rating conventions and standard archery adjustment rules-of-thumb, as published by the Ashby Bowhunting Foundation's Arrow Speed Calculator methodology and widely cited archery-industry chronograph adjustment tables (ArcheryTalk IBO rating discussions). Kinetic energy formula is the standard archery-industry KE = mv²/450,240 constant.

Worked Examples

Typical Whitetail Hunting Setup

IBO Rated Speed: 330 fps
Draw Length: 28 in
Draw Weight: 60 lb
Arrow Weight: 420 gr
String Accessories: 0 gr

250 fps, 58.30 ft-lbs KE

Draw length: (28-30)×10 = -20 fps. Draw weight: (60-70)×2 = -20 fps. Baseline arrow weight = 5×60 = 300 gr, so deviation = 420-300 = 120 gr → -(120÷3) = -40 fps. Total: 330-20-20-40 = 250 fps. KE = (420×250²)÷450,240 = 58.30 ft-lbs — comfortably above the 25-41 ft-lbs typically recommended for deer-sized game.

IBO Baseline Setup (Sanity Check)

IBO Rated Speed: 340 fps
Draw Length: 30 in
Draw Weight: 70 lb
Arrow Weight: 350 gr
String Accessories: 0 gr

340 fps, 89.86 ft-lbs KE

Every input matches the IBO test standard exactly, so all four adjustments are zero and the estimated speed equals the bow's rated IBO speed unchanged — this is the baseline case the whole formula is built around. KE = (350×340²)÷450,240 = 89.86 ft-lbs.

Youth / Light Draw Weight Bow

IBO Rated Speed: 320 fps
Draw Length: 27 in
Draw Weight: 50 lb
Arrow Weight: 300 gr
String Accessories: 10 gr

230 fps, 35.25 ft-lbs KE

Draw length: (27-30)×10 = -30 fps. Draw weight: (50-70)×2 = -40 fps. Baseline arrow weight = 5×50 = 250 gr, deviation = 300-250 = 50 gr → -(50÷3) = -16.67 fps. String accessories: -(10÷3) = -3.33 fps. Total: 320-30-40-16.67-3.33 = 230 fps. KE = (300×230²)÷450,240 = 35.25 ft-lbs — still enough for deer per most state minimums, but with less margin.

Fast Modern Hunting Bow, Near-Baseline Draw

IBO Rated Speed: 350 fps
Draw Length: 29 in
Draw Weight: 70 lb
Arrow Weight: 380 gr
String Accessories: 5 gr

328.33 fps, 90.98 ft-lbs KE

Draw length: (29-30)×10 = -10 fps. Draw weight: (70-70)×2 = 0 fps. Baseline arrow weight = 5×70 = 350 gr, deviation = 380-350 = 30 gr → -(30÷3) = -10 fps. String accessories: -(5÷3) = -1.67 fps. Total: 350-10+0-10-1.67 = 328.33 fps. KE = (380×328.33²)÷450,240 = 90.98 ft-lbs — well into the elk/large-game penetration range.

Light Target/3D Arrow, Long Draw

IBO Rated Speed: 310 fps
Draw Length: 31 in
Draw Weight: 45 lb
Arrow Weight: 200 gr
String Accessories: 0 gr

278.33 fps, 34.41 ft-lbs KE

Draw length: (31-30)×10 = +10 fps. Draw weight: (45-70)×2 = -50 fps. Baseline arrow weight = 5×45 = 225 gr, deviation = 200-225 = -25 gr → -(-25÷3) = +8.33 fps (lighter arrow gains speed). Total: 310+10-50+8.33 = 278.33 fps. KE = (200×278.33²)÷450,240 = 34.41 ft-lbs. A flat, fast trajectory typical of a target/3D setup rather than a hunting arrow.

How to Use This Calculator

1

Find your bow's IBO rated speed

Check the spec sheet, manufacturer website, or the sticker on the bow's riser. This is the speed tested at 70 lb / 30 in draw / 350-grain arrow — not your real-world speed yet.
2

Enter your actual draw length and draw weight

Use your measured draw length (have a pro shop check it if unsure) and your bow's set draw weight, not its maximum rated weight.
3

Enter your total finished arrow weight

Weigh the complete arrow — shaft, point/broadhead, insert, fletching, and nock — on a grain scale, or add up the component weights from your build sheet.
4

Add any string accessory weight (optional)

If you run string silencers, a peep sight, or a kisser button, enter the combined weight in grains. Leave at 0 if you're not sure — the effect is small.
5

Read your estimated speed and kinetic energy

The calculator applies all four IBO adjustment rules and shows your estimated real-world arrow speed plus kinetic energy at that speed.

What Each Value Means

IBO Rated Speed (feet per second (fps)): The speed printed on a compound bow's spec sheet, tested under the International Bowhunting Organization's fixed standard: 70 lb draw weight, 30 in draw length, a 350-grain arrow, and no string accessories. It's a manufacturer benchmark for comparing bows, not a prediction of what any individual archer will actually shoot.
Estimated Arrow Speed (feet per second (fps)): The IBO rated speed adjusted for your actual draw length, draw weight, arrow weight, and string accessory weight using standard archery-industry per-unit adjustment rules. A rule-of-thumb estimate, not a chronograph-verified number.
Kinetic Energy (KE) (foot-pounds (ft-lbs)): A measure of the arrow's momentum at impact, calculated from arrow weight and velocity. Used by bowhunters and some state wildlife agencies as a rough guide for whether an arrow setup carries enough energy to ethically and effectively take a given size of game.

Frequently Asked Questions

What is IBO speed, and why isn't my actual arrow speed the same number?

IBO (International Bowhunting Organization) speed is the number printed on every compound bow's spec sheet, measured under one fixed test condition: 70 lb draw weight, 30 in draw length, a 350-grain arrow, and nothing on the string. Almost no one shoots that exact setup — most archers draw less weight, a different length, and a heavier hunting arrow — so the real number is always lower than the advertised IBO speed. This calculator applies the standard adjustment rules to translate the marketing number into a realistic estimate for your actual setup.

How much does draw length really affect arrow speed?

About 10 fps per inch, and it's usually the single biggest factor separating your real speed from the advertised IBO number. Draw length is fixed by your arm span and shooting form, not a tuning choice, so a 27-inch draw archer shooting a bow rated at 330 fps IBO starts about 30 fps below that number before any other adjustment — even before accounting for draw weight or arrow weight.

How much kinetic energy do I need for bowhunting?

There's no single legal minimum in most US states, but the archery industry's widely cited rule-of-thumb guidance is roughly 25 ft-lbs minimum for small game, 25-41 ft-lbs for deer-sized game, 42-65 ft-lbs for elk and black bear, and 65+ ft-lbs for the largest dangerous game like brown bear or African plains game. These are guidelines, not law — always check your specific state or country's regulations, and remember that shot placement and broadhead sharpness matter more than raw kinetic energy.

Why would I want a heavier, slower arrow instead of a lighter, faster one?

Heavier arrows carry more kinetic energy and momentum at the same draw weight, which generally means deeper penetration, a quieter shot (less energy left over to vibrate through the bow), and less sensitivity to minor tuning imperfections. Lighter arrows fly flatter and faster, which helps with judging distance at longer range, but sacrifice penetration and forgiveness. Most bowhunters land somewhere in the middle — the 5-6 grains-per-pound range this calculator's baseline is built on.

Do string accessories like a peep sight or silencers actually slow my arrow down?

Yes, slightly. Anything added to the bowstring itself — a peep sight, string silencers, a kisser button — adds mass the string has to accelerate on every shot, at roughly 1 fps of speed loss per 3 grains added. It's a small effect compared to draw length or draw weight, but it's real and it's why serious speed-focused archers use lightweight peeps and minimal string silencers.