Estimate your arrow’s launch speed from a bow speed rating (IBO or ATA/AMO) using draw length, peak draw weight, arrow weight, and optional string/accessory weight, then see kinetic energy and momentum. You also get a transparent breakdown of each speed adjustment so the estimate is not a black box.
Advanced options
How to use our Arrow Speed Calculator
- In "What do you want to calculate?", choose "Estimate arrow speed from IBO/ATA rating" (use this if you have an advertised rating).
- Set "Speed rating standard" to match the rating you are entering: IBO (70 lb, 30 in, 350 gr) or ATA/AMO (60 lb, 30 in, 540 gr).
- Enter your "Bow speed rating (fps)" exactly as listed for your bow under that standard.
- Enter your actual "Draw length (in)" (the bow setting or a shop measurement, not wingspan math).
- Enter your actual "Peak draw weight (lb)" at your current limb-bolt setting (not the max printed on the limbs).
- Enter total finished "Arrow weight (grains)" including point/broadhead, insert, nock, vanes, and shaft [1].
- Optional: Open Advanced options and enter "Weight on bowstring (grains)" for peep, D-loop, silencers, etc. If unsure, start with a small estimate and adjust later.
- Optional: Pick an "Adjustment rule set" (Conservative vs Typical) and your "Speed output unit" display preference.
- Click "Calculate".
- Sanity-check: In "Speed adjustment breakdown", confirm the directions look right (heavier arrows and more string weight should reduce speed; longer draw length and higher draw weight should increase speed). If the reliability note says low confidence, treat the number as a rough estimate.
Common mistakes and quick fixes
Mistake: Mixing standards (entering an IBO-style rating but selecting ATA/AMO, or the other way around).
Fix: Match "Speed rating standard" to the rating source you have. If the reliability note warns the rating looks unusual for that standard, double-check the spec sheet.
Mistake: Using only the shaft weight for "Arrow weight (grains)" and forgetting the point/broadhead and other parts.
Fix: Enter the total finished arrow weight (complete arrow) [1]. If you are guessing, you will usually be closer by rounding up than rounding down.
Mistake: Entering draw length or draw weight from a catalog instead of your current bow settings.
Fix: Use your actual "Draw length (in)" and your actual "Peak draw weight (lb)" as the bow is set up today. Even small changes can move the estimate a lot.
Mistake: Leaving "Weight on bowstring (grains)" at 0 even though you have a peep, D-loop, and/or string silencers installed.
Fix: Add an estimate (for example, 10 to 20 grains) and compare the new result to the old one using the breakdown so you can see how sensitive speed is to string weight.
Mistake: A typo that makes the model unusable (for example 3300 fps, or 40 grains instead of 400), leading to N/A or a wildly high/low result.
Fix: Recheck each required field for a missing digit or wrong unit, then recalculate. If you still get N/A, bring the setup closer to the chosen standard or measure with a chronograph.
Mistake: Treating the estimate as guaranteed real speed for every bow type and setup.
Fix: Use it as a planning number. If your bow is not a compound with a published rating, or if your setup is far from the baseline, expect bigger error and rely on measured speed when it matters.
Definitions
IBO speed rating: A published compound-bow speed measured under a standard baseline (70 lb peak draw weight, 30 in draw length, 350 grain arrow). Your real setup usually differs, so your real speed will differ too.
ATA/AMO speed rating: Another industry baseline that uses a heavier arrow and lower peak draw weight than IBO (commonly shown as 60 lb, 30 in, 540 grain). For the same bow, ATA/AMO ratings are usually lower than IBO ratings.
Bow speed rating (fps): The advertised speed in feet per second that your bow is rated at under the selected standard. The calculator starts from this number.
Draw length (in): How far the bow is set to draw, in inches. Ratings often assume 30 inches, so shorter draw lengths usually reduce estimated speed.
Peak draw weight (lb): The maximum draw weight your bow reaches, in pounds. Ratings assume a specific peak weight (often 70 lb for IBO).
Arrow weight (grains): Total finished arrow weight in grains (gr), including point/broadhead and all components [1].
Weight on bowstring (grains): Extra weight attached to the string (peep sight, D-loop, silencers, nock set). More string weight usually lowers speed.
Kinetic energy (ft-lbf, J): Energy of motion at launch, based on arrow weight and speed. It increases with speed squared, so a small speed change can noticeably change energy.
Momentum (slug-ft/s, kg-m/s): Mass times speed at launch. Heavier arrows can have higher momentum even if they are slower.
Speed adjustment breakdown: The list of fps added or subtracted for draw length, draw weight, arrow weight, and string/accessory weight based on the selected rule set.
Estimate reliability note: A short message that flags common reliability problems, like inputs that are far from the chosen standard or a rating value that looks mismatched to the selected standard.
Methodology
Overview: The calculator estimates launch speed (near the bow) by starting from a published speed rating (IBO or ATA/AMO) and applying rule-of-thumb adjustments for how your draw length, peak draw weight, arrow weight, and string/accessory weight differ from that standard. It then converts speed units and computes kinetic energy and momentum. This is an estimate, not a chronograph measurement [2].
1) Baseline values (by standard): For IBO, baseline draw length is 30 in, baseline peak draw weight is 70 lb, and baseline arrow weight is 350 gr. For ATA/AMO, baseline draw length is 30 in, baseline peak draw weight is 60 lb, and baseline arrow weight is 540 gr.
2) Speed estimate (rating plus adjustments):
speed_est_fps = rating_fps + adj_draw_length + adj_draw_weight + adj_arrow_weight + adj_string_weight
adj_draw_length = (draw_length_in - baseline_draw_in) * k_dl
adj_draw_weight = (peak_draw_weight_lb - baseline_weight_lb) * k_dw
adj_arrow_weight = (baseline_arrow_gr - arrow_weight_gr) * k_ag
adj_string_weight = - string_accessory_weight_gr * k_sg
The coefficients k_dl, k_dw, k_ag, and k_sg are the selected "Adjustment rule set" (Conservative or Typical). Because real bows vary in efficiency and published rules of thumb differ, the calculator shows your exact per-factor changes in the "Speed adjustment breakdown" so you can see what drove the result.
3) Speed unit conversions:
speed_ms = speed_fps * 0.3048
speed_mph = speed_fps * (3600/5280)
speed_kmh = speed_ms * 3.6
4) Kinetic energy and momentum:
KE_ftlb = (arrow_weight_gr * speed_fps^2) / 450240
KE_J = KE_ftlb * 1.3558179483314004
mass_kg = arrow_weight_gr * 0.00006479891
p_kgms = mass_kg * speed_ms
mass_lb = arrow_weight_gr / 7000
mass_slug = mass_lb / 32.174
p_slugfps = mass_slug * speed_fps
Worked mini-example (numbers): Suppose you select IBO and enter rating_fps = 330, draw_length_in = 28, peak_draw_weight_lb = 60, arrow_weight_gr = 400, and string_accessory_weight_gr = 15. The calculator first computes each adjustment from the difference between your input and the IBO baseline (30 in, 70 lb, 350 gr), then adds them to 330 fps to get speed_est_fps. It then converts the speed and computes kinetic energy and momentum from that estimated speed.
Assumptions and limits: Best fit is a compound bow with a real rating under the standard you selected. Results can differ from real chronograph readings due to bow efficiency, tune (cam timing, timing marks), string/cable condition, arrow spine and tune, release style, and chronograph placement [2]. If your inputs are far from the baseline (very light/heavy arrows, large changes from 30 in draw length, or an unusual rating for the selected standard), treat the output as lower confidence and consider measuring speed directly.