Why Compound Bow Specs Actually Matter
Walk into a bow shop and you'll see specs like "70 lb / 26–30" / ATA 32" / 80% let-off / 330 FPS IBO." Each number has real consequences for whether the bow fits your body, is legal for hunting in your state, and whether you can shoot it accurately. A bow with too much draw weight causes flinching and injury. Wrong draw length destroys form before it starts.
Unlike buying a rifle or fishing rod, compound bow selection is intensely personal — the same model can be perfect for one shooter and wrong for another based purely on body measurements. This guide decodes every key spec and tells you what numbers to target for your use case.
Draw Weight: The Most Misunderstood Spec
Draw weight is the peak force (in pounds) required to pull the bowstring to full draw. It directly determines arrow speed, kinetic energy, and whether you can legally hunt big game in your state.
| Draw Weight | Best For | Legal for Deer? | Est. Arrow Speed |
|---|---|---|---|
| 20–30 lbs | Youth, intro target | No (most states) | 180–220 fps |
| 30–40 lbs | Adults learning, small game | Some states | 220–260 fps |
| 40–50 lbs | Deer, turkey, hunting | Yes (most states) | 260–290 fps |
| 50–60 lbs | All big game, elk at range | Yes | 290–320 fps |
| 60–70 lbs | Long-range, large game | Yes | 310–340+ fps |
Key insight: More draw weight isn't always better. 50–60 lbs is the ideal range for most hunters. You'll get complete pass-throughs on whitetail deer while avoiding the shoulder fatigue and form breakdown that comes with maxing weight. Studies show most bowhunting shots are taken under 30 yards — shot placement matters far more than raw kinetic energy at those distances.
Draw Length: The Critical Fit Measurement
Draw length is the distance from the grip to the nock point at full draw. Get this wrong and every shot will be inconsistent. Too long = overextended, poor anchor, accuracy suffers. Too short = elbow bent wrong, string slaps your arm, torque introduced.
How to Measure Your Draw Length
- Stand naturally with arms extended straight out to each side (T-position)
- Measure your wingspan: fingertip to fingertip across your back
- Divide by 2.5 — this is your approximate draw length in inches
- Example: 70-inch wingspan ÷ 2.5 = 28-inch draw length
This formula works for most people, but always verify at a pro shop with an actual bow. Torso proportions vary and a few half-inches makes a meaningful difference.
| Height | Estimated Draw Length |
|---|---|
| 5'0"–5'4" | 25"–26.5" |
| 5'5"–5'8" | 27"–28" |
| 5'9"–6'0" | 28.5"–29.5" |
| 6'1"–6'4" | 30"–31" |
ATA Length: Maneuverability vs. Forgiveness
ATA (Axle-to-Axle) measures the distance between the two cam pivot points. It determines the physical length of the bow and has real implications for where and how you hunt.
- Short ATA (28–32"): Easier to maneuver in tree stands, ground blinds, and tight cover. String angle at full draw is more acute, which can cause finger pinch without a mechanical release.
- Medium ATA (32–36"): Sweet spot for most hunters. Manageable in the field and more forgiving of torque and form errors.
- Long ATA (36–42"): Maximum accuracy and forgiveness. Preferred by 3D and target shooters. Awkward in tree stands.
Let-Off Percentage: What You Actually Hold at Full Draw
Let-off is the percentage of peak draw weight the cam system reduces at full draw. On a 70 lb bow with 80% let-off, you hold only 14 lbs at full draw. This mechanical advantage is unique to compound bows — traditional and recurve bows have zero let-off.
| Let-Off | Hold Weight (70 lb bow) | Best For |
|---|---|---|
| 65% | 24.5 lbs | 3D target, solid back-wall feel |
| 75% | 17.5 lbs | Balanced hunting/target use |
| 80% | 14 lbs | Most hunters — easy hold at full draw |
| 90% | 7 lbs | Accessibility needs, crossover disciplines |
For hunting, 80% let-off is the standard sweet spot. It lets you hold at full draw while waiting for an ethical shot without muscle fatigue. Some states cap let-off at 65% for certain seasons — always check your local regulations before buying.
Arrow Speed: IBO vs. Real-World FPS
IBO (International Bowhunting Organization) speed ratings are measured under ideal conditions: 70 lb draw weight, 30" draw length, 350-grain arrow. Your real-world speed will likely be 20–40 fps slower depending on your setup, accessories, and arrow weight. Don't buy a bow based on IBO speed claims alone.
For hunting: 250–280 fps is plenty for ethical shots on big game within 50 yards. Speed beyond that adds noise, vibration, and tuning complexity without meaningful lethality gains at realistic bowhunting distances.
Top Beginner Compound Bow Picks
Essential Accessories
A bare bow is just the start. You'll also need a mechanical release aid, arrow rest, bow sight, correctly spined arrows, and a rangefinder for hunting. See our Arrow Selection Guide, Bow Sight Guide, and Rangefinder Guide for detailed breakdowns.
Common Buying Mistakes
Frequently Asked Questions
What draw weight do I need for deer hunting with a compound bow?
Most states require a minimum of 40 lbs for deer, but 50–60 lbs is the practical sweet spot. At 50 lbs with a quality broadhead, you'll achieve complete pass-throughs on whitetail at typical archery ranges under 40 yards. Going heavier doesn't significantly increase lethality but does increase fatigue and form breakdown.
How do I measure my draw length for a compound bow?
Stand with arms outstretched in a T. Measure your wingspan (fingertip to fingertip) and divide by 2.5. For example, a 70-inch wingspan = 28-inch draw length. Have a pro shop verify this in person — torso proportions vary and a few half-inches matters.
What is let-off on a compound bow and why does it matter?
Let-off is the percentage of peak draw weight you hold at full draw. An 80% let-off on a 60 lb bow means you hold only 12 lbs at full draw, making it much easier to stay steady for longer shots while waiting for the right moment in the field.
What does ATA mean on compound bows?
ATA stands for Axle-to-Axle length — the distance between the two cam pivot points. Shorter ATA (28–32") is more maneuverable in tree stands and ground blinds. Longer ATA (34–38") is more forgiving of form errors and preferred for target shooting. Most hunting bows fall in the 30–34" range.
Sources & Further Reading
- Archery Trade Association. "IBO Speed Standard Testing Protocol." archerytrade.org
- National Bowhunter Education Foundation. "Bowhunter Education Manual." nbef.org
- Pope & Young Club. "Bowhunting Records and Ethics." pope-young.org
- Lancaster Archery Supply. "How to Determine Draw Length." lancasterarchery.com
- Bowhunting.com. "Compound Bow Setup Guide for Beginners." bowhunting.com
