Every compound bow has a draw length setting. The number is stamped on the module, printed on the spec sheet, and treated by most archers as a property of the bow. It is not. The bow does not care what draw length it is set to. The bow will do exactly what the archer asks of it at any setting the cams permit.
The number matters because you are set to a specific length, whether you know it or not. Your skeleton has a full-draw geometry that stacks bone against bone and holds a bow with almost no muscular effort. The right draw length puts you into that geometry. The wrong draw length — off by even a quarter of an inch — lands you somewhere near it, and asks the small stabilizing muscles of your shoulder to make up the difference. Every shot. Every session. Forever, if you don't fix it.
This is why draw length adjustments are the single most consequential setup change on a compound bow, and it is why so many archers plateau at a level they cannot explain. The bow is fine. The tune is fine. The archer's own draw length has never been dialed to their skeleton.
Alignment is a bone problem, not a muscle problem
Coaching manuals from Archery Australia, USA Archery, and every serious recurve federation in the world agree on one principle before they agree on anything else: at full draw, the load of the bow should travel primarily through bones, not through muscles. The muscles are there to hold the bones in position. If the bones are stacked correctly, the muscles do almost nothing.
Concretely: the bow-side arm should transmit the resistance of the bow through the humerus, into the scapula (shoulder blade), across to the thoracic spine, down through the trunk, and into the ground through the stance. The drawing arm should have its elbow behind the line of the arrow, so the drawing scapula can glide toward the spine using the large back muscles (the rhomboids and lower trapezius) rather than the smaller shoulder and arm muscles.
When this stack is correct, holding a 60-pound bow at 15 pounds of let-off feels like holding a book. When the stack is even slightly off, the same 15 pounds feels like a workout, and the workout is being done almost entirely by the rotator cuff — a group of four small muscles that were not designed to be prime movers for anything, and that will complain, then twinge, then eventually fail, if you keep asking them to.
Where to start: wingspan divided by 2.5
The standard starting estimate for draw length is your wingspan in inches, divided by 2.5. Measure fingertip to fingertip with your arms extended out to the sides, relaxed but straight. Divide by 2.5. That is your AMO draw length estimate to the nearest quarter inch or so.
Someone with a 70-inch wingspan lands at 28 inches. Someone with a 66-inch wingspan lands at 26.4 inches. This is a body proportion calculation, not a personal preference, because the formula is trying to predict where your natural full-draw alignment lives — and your natural alignment lives at a length your skeleton dictates, not a length you choose.
The wingspan formula is a starting point. It is not the answer. The answer comes from watching what your body does at full draw and adjusting the mods until the geometry lands where it wants to land. But the wingspan number is almost always within a half inch of correct, and it will save you from starting a whole draw-length hunt at three inches wrong.
What correct full-draw geometry looks like
If you could freeze an archer at the moment of release and photograph them from directly above, you would see something specific.
The bow-side shoulder is low and back. It has not risen to meet the effort of holding the bow. It sits in its natural socket position, packed against the ribcage. The humerus enters the shoulder at an angle that transmits force straight through the joint capsule rather than shearing across it.
The bow arm is rotated, not locked. The elbow is not hyperextended. It is rotated inward — the crease of the elbow points up and slightly outward rather than directly at the archer's face. This rotation clears the string path from the forearm (so no string slap on release) and engages the triceps to keep the arm stable without muscular effort at the biceps.
The drawing forearm is roughly horizontal or slightly rising. The drawing elbow sits at or slightly behind the line of the arrow, seen from above. This position lets the scapula glide toward the spine as the back muscles contract, rather than forcing the shoulder to rotate to reach the wall.
The scapulae are flush against the ribcage. Neither is "winging" — sticking out at the medial edge — which is the tell-tale sign that the shoulder blade has lost contact with the rib cage and the small stabilizers are working overtime.
The head is vertical and neutral. The string touches the nose or the corner of the mouth as a reference point, not because the archer has chased the string with their head. Chin down slightly, eye behind the peep without craning.
Everything about this position looks unforced. That is not because the archer is a magician. It is because they have found the geometry their skeleton wants to be in, and the bow — set to a draw length that matches — is letting them be there.
Too long: the failure mode most archers grow up with
Long is the more common mistake, especially in adult male archers, and there are two reasons for that. First, most people want a longer draw length because it correlates loosely with speed and, uncharitably, with looking impressive at the range. Second, most people were fit for a bow at a point in their life when they had less shoulder mobility than they thought they did, and they never revisited the number as their form matured.
Here is what a bow set an inch too long does to a body:
The bow arm goes into hyperextension. With no more length available in the drawing arm's natural travel, the archer's body finds the extra inch by locking the bow arm — pushing the elbow into a bone-on-bone extended position that hurts on release, invites string slap on the inside of the forearm, and transmits every shot's vibration directly through the elbow joint into the rotator cuff.
The bow shoulder rises to reach the wall. When the bow arm can't extend any further, the shoulder blade tries. It rotates up, disengages from the ribs, and the whole shoulder complex becomes a compensation zone. The rotator cuff — specifically the supraspinatus, the muscle running across the top of the shoulder — starts doing the work of holding the bow in space. It is not equipped for that job.
The head chases the string. Because anchor happens further back than the archer's natural position wants, they either drift their head forward to reach the peep, or they cant their head into the string in ways that make the peep alignment change slightly at every shot. Peep rotation issues that look like a string problem are often a draw-length problem.
The release lands early or collapses. With the shoulder complex already at the edge of its range, there is no more back tension to develop through the shot. The archer either releases before they reach a proper wall, or their back gives out and they creep forward off the wall. Neither is repeatable.
Too short: the failure mode that hides better
Short is less common but easier to miss, because a bow that is slightly too short does not usually hurt. It just underperforms. And the archer, having no obvious discomfort, blames the bow, the arrows, or themselves.
What a bow set a half inch too short does:
The drawing arm folds too far. The drawing elbow ends up ahead of the arrow line rather than behind it, and the scapula can no longer glide toward the spine using the big back muscles. Instead, the small posterior deltoid and the rear cuff pick up the load. The archer feels the effort in their shoulder, not their back.
The bow shoulder bunches. Without the reach demanded by the correct draw length, the bow shoulder pulls slightly forward and upward — the bones lose their stack. The archer compensates by pushing harder into the bow with the bow arm, which introduces torque, which shows up as arrow inconsistency the tune cannot cure.
Anchor floats. The archer's natural anchor reference lands past where the string wants to be. Either they chase the anchor forward with their head, or they settle for a short anchor that changes shot to shot depending on how much they concentrate on it.
Back tension has no room to develop. A bow set too short reaches the wall before the back muscles finish their contraction. The wall arrives, the release has to happen, and back tension — the muscular pattern that produces a clean, surprise release — never gets to complete its motion. The archer either punches the trigger to end the shot, or over-holds while trying to build back tension that has no more travel to give.
The compound-specific problem: the wall is not negotiable
On a recurve bow, a draw length that is slightly wrong is a draw length that the archer can partially work around. Recurves don't have a hard wall — the archer can pull to whatever position their body wants and release from there. Form suffers, but the geometry can adapt to the archer.
Compounds don't work that way. The draw stops fix the string's rearward travel to the exact position the cams were set to reach. If the mods say 28.0 inches and your body wants 28.375, you meet a wall at 28.0 and no amount of pulling harder gets you to your natural geometry. You either shoot from a position slightly ahead of where you want to be, or you hyperextend to reach the position the mods have chosen for you.
This is why compound draw length is worth measuring precisely and worth adjusting until it lands right. The recurve archer can absorb a small mismatch by adjusting their body. The compound archer, at every shot, has their body adjusted by the mismatch. The bow imposes a geometry. If it is the wrong geometry, the archer's body accommodates the wrongness silently — and pays for it in overuse patterns you cannot see coming.
How the shoulder pays the bill
The rotator cuff is a group of four small muscles — the supraspinatus, infraspinatus, teres minor, and subscapularis — whose job is to hold the head of the humerus centered in the shoulder socket during large arm movements. They are stabilizers, not prime movers. They are physically small. They tire easily.
Peer-reviewed sports-medicine literature on archery injuries points at the rotator cuff overuse pattern with unusual consistency. When scapular positioning fails during the draw — either because the archer never learned the correct back-tension sequence, or because their bow's draw length forces them out of alignment — the rotator cuff picks up the load. And because archery is a high-repetition, low-instantaneous-load activity, the injury does not announce itself with a moment of trauma. It arrives as a slowly worsening ache in the front of the shoulder that the archer blames on practice volume.
Practice volume is not the cause. Practice volume is what exposes the cause. The cause is a stabilizer muscle being asked to be a prime mover, session after session, in a geometry the archer's draw length is silently enforcing.
How to know when the draw length is right
You cannot self-diagnose draw length by feel alone. Every archer's proprioception is calibrated to whatever geometry they have been living in — even a wildly incorrect draw length feels normal after enough repetition. The feedback has to come from an outside view.
Three practical ways to check, in decreasing order of reliability:
- Have a coach or another experienced archer watch you from directly behind and from above. The alignment cues are geometric — bow shoulder low, drawing elbow behind the arrow line, head vertical, scapulae flat — and someone with the right vantage will spot the failure modes in one or two shots.
- Shoot video from behind at eye level. Slow motion at full draw is enough. Look for the bow shoulder rising, the bow arm locking straight, the head chasing forward or tilting into the string.
- Watch your own release in a mirror at close range with a training aid, or work with a form specialist. This is less good than the first two because you are still inside the geometry you are trying to observe, but it is better than feel alone.
The specific things to check for at full draw:
- Is the bow shoulder low, or has it risen toward the ear?
- Is the bow arm elbow rotated (crease pointing up) or locked flat?
- Is the drawing elbow behind the arrow line, seen from directly above?
- Are the shoulder blades flush against the ribcage, or is either winging out?
- Is the head vertical with the string touching a natural reference, or is the head chasing the string?
- Does the release feel like a completion of back tension, or like a punch, a collapse, or a hold?
Any of these being wrong points at a draw-length mismatch as the first suspect. It is not the only possible cause — form errors independent of length exist — but it is the highest-impact cause, and the one to rule out before chasing anything else.
Why this article exists on a bowstring builder's website
Because a properly built string cannot fix a body being asked to shoot from the wrong geometry. Because peep rotation blamed on a poorly stretched bundle is often a head-chasing-string problem in disguise. Because the target archer who cannot break through their plateau is, most often, an archer whose draw length is off by three-eighths of an inch and whose form is compensating for it perfectly at 40 yards and imperfectly at 70.
The bow and the archer are one mechanical system. Axial spends a lot of time on the bow half of that system, and the strings that hold it together, because that is what we build. But every string leaves the shop and gets installed on a bow that is going to be drawn by a body. If the body is being asked to work at the wrong length, no amount of string-building excellence will make up the difference.
Fix the number first. Everything else you tune afterward will actually stay tuned.
Connections
See Bow geometry for how AMO draw length is measured on a draw board and why 28-inch mods measure 26.25 pivot-to-nock. See Cam timing for what to check after draw length is verified. See Peep rotation for the specific failure mode that a chasing head produces in an otherwise correctly-built string.
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Published 2026-07-04 · Axial Bowstrings