Draw Length Calculator (Wingspan Method)
Draw length in inches equals your wingspan in inches divided by 2.5, rounded to the nearest half inch. A 70 inch wingspan gives a 28 inch draw length.
Draw length is the first measurement to get right, because arrow length, spine, arrow speed and even your sight tape are all downstream of it. The standard estimate is wingspan divided by 2.5, rounded to the nearest half inch, and it is accurate enough to order a bow with. This calculator runs that plus a height cross-check so you can see whether the two agree.
The formula and where the 2.5 comes from
Draw length equals wingspan divided by 2.5. Measure fingertip to fingertip with both arms extended sideways at shoulder height, palms facing forward, standing relaxed against a wall. Do not stretch. Stretching is the single biggest source of error in this measurement and it reliably produces a draw length half an inch too long.
The constant 2.5 is empirical rather than derived. The Archery Manufacturers Organisation measured large numbers of archers shooting from a repeatable anchor and found that arm span predicted the drawn geometry of a bow closely enough to publish a divisor. It holds because both quantities scale with skeletal size. It breaks down at the edges: archers with unusually long arms relative to torso, or unusually short ones, can sit up to a full inch off the formula, which is exactly what the height cross-check is for.
Wingspan to draw length chart
Rounded to the nearest half inch, which is the increment most compound modules and draw stops adjust in.
| Wingspan | Draw length | Typical height | Who this usually fits |
|---|---|---|---|
| 57 in | 23.0 in | 4 ft 9 in | Youth archers |
| 60 in | 24.0 in | 5 ft 0 in | Youth and small-framed adults |
| 62.5 in | 25.0 in | 5 ft 2 in | Smaller adult archers |
| 65 in | 26.0 in | 5 ft 5 in | Common adult women's draw |
| 67.5 in | 27.0 in | 5 ft 7 in | Very common across both sexes |
| 70 in | 28.0 in | 5 ft 10 in | The industry default draw length |
| 72.5 in | 29.0 in | 6 ft 0 in | Taller adult men |
| 75 in | 30.0 in | 6 ft 3 in | The IBO test standard |
| 77.5 in | 31.0 in | 6 ft 5 in | Longer than many bows adjust to |
The height cross-check
For most people wingspan and height are within an inch or two of each other, so height divided by 2.5 gives a second independent estimate. When the two agree within half an inch, you can order with confidence. When they disagree by an inch or more, trust the wingspan number, because it is the measurement that actually describes how far your hands separate at full draw, and then get it confirmed in person before you spend money on modules.
People who commonly see the two diverge include swimmers and climbers, who tend to have wingspans noticeably longer than their height, and anyone with a long torso relative to their limbs. Neither is a problem. It just means the shortcut is less reliable for you specifically.
AMO draw length, and why bows are labelled the way they are
Every modern compound is specified in AMO draw length: the distance from the nock groove on the string at full draw to the pivot point of the grip, plus 1.75 inches. The pivot point is the deepest part of the throat of the grip, and on almost every riser it sits directly below the berger hole where your rest mounts.
That 1.75 inch addition is a historical convention, not a physical distance you can point at. It exists so the draw length number roughly matches the arrow length archers used before centreshot rests. The practical consequence worth remembering is this: at full draw, the distance from your nock to your rest is your draw length minus 1.75 inches. That single fact is what the arrow cut length calculator is built on, and it is why an arrow can be shorter than your draw length and still be perfectly safe.
On a compound, the d-loop and release aid sit between your anchor and the string, so they are part of the measurement whether you account for them or not. A wrist strap release adds more length than a handheld, and switching between the two can shift your effective draw by a quarter inch or more. Settle on the release you intend to keep before you finalise a draw module.
How a pro shop verifies it
The shop method is a draw check arrow: an overlong arrow marked in half inch increments, shot on a bow set near your estimate. You come to full draw with your own release and your own anchor, and the shop reads the mark at the back of the riser, then adds the AMO convention. Because you are measured shooting rather than standing against a wall, it captures your actual anchor, your head position, and how much you engage your back.
Expect the shop number to come in slightly shorter than the wingspan formula for most people, often by a quarter to half an inch. That is normal and it is a good thing. The formula does not know that you will eventually learn to pull with your back rather than your arm, and that change alone shortens most archers.
What going too long actually costs you
Overdrawing is the most common fitting error in archery, and the reasons are unglamorous: a longer draw stores more energy, so it looks better on paper, and a bow set too long simply feels more powerful. What it does in practice is lock the bow arm elbow, push the anchor rearward past the jaw, and force a head lean that changes every time you get tired. It also flattens the string angle, which is why string slap on the forearm is usually a draw length symptom rather than a form one.
A half inch too short costs about five feet per second and almost nothing else. A half inch too long costs group size permanently. When in doubt, and particularly when you are new, go short.
Recurve and traditional differences
Recurve and longbow draw lengths are measured the same way, but they matter differently. Marked limb poundage on a recurve is measured at a 28 inch draw, so drawing 30 inches means you are pulling roughly five pounds more than the sticker says, at about 2.5 pounds per inch. That directly changes the shaft you need, which is why the arrow spine calculator asks for both draw weight and draw length rather than weight alone. Traditional archers also tend to run longer arrows for shelf clearance, which weakens dynamic spine further.
Related tools
- Arrow spine calculator: the first thing your draw length feeds into
- Arrow cut length calculator: turn this number into a shaft length by rest type
- Draw weight calculator: the other half of a correct fit
- Arrow speed calculator: see what each inch of draw is worth in fps
- Best archery rangefinders: once the bow fits, distance is the next variable
Frequently asked questions
How do I measure my draw length at home?
Stand naturally, stretch both arms out sideways with palms forward, and have someone measure fingertip to fingertip across your back. Divide that wingspan in inches by 2.5 and round to the nearest half inch. A 70 inch wingspan gives a 28 inch draw length. This is the AMO estimate and it lands within half an inch for most adults, which is close enough to order a bow module.
Why divide wingspan by 2.5?
It is an empirical constant, not physics. The Archery Manufacturers Organisation measured large numbers of archers at a repeatable anchor and found that the distance from the nock groove to the grip pivot point plus 1.75 inches tracked wingspan closely enough to predict it by dividing by 2.5. It works because arm span and the geometry of a drawn bow scale together across body sizes.
What is the difference between AMO and true draw length?
AMO draw length is measured from the nock groove at full draw to the pivot point of the grip, plus 1.75 inches. True draw length is that same measurement to the back of the riser. Modern bows are all specified in AMO, so when a bow is sold as a 28 inch draw it means AMO. The 1.75 inch addition exists so the number roughly matches the old arrow length convention.
What happens if my draw length is too long?
Too long is by far the more common error and the more damaging one. It forces the bow arm to lock, pushes the string hand behind the anchor, and creates a rearward head lean that ruins consistency. It also flattens the string angle so the string touches your face or arm. Most archers who shoot a half inch short gain accuracy immediately, and few notice any speed loss.
Does draw length change what arrows I need?
Yes, indirectly but strongly. Draw length sets your arrow cut length, and arrow length is the largest single influence on dynamic spine. An inch of extra arrow behaves roughly like adding five pounds of bow weight. Draw length also changes stored energy, worth about ten feet per second per inch, so it moves both your spine requirement and your finished arrow speed.
Should I measure draw length with a release aid attached?
For a compound, yes. The d-loop and the release together add length between your anchor and the string, and a wrist strap release adds more than a handheld one. A pro shop measures your draw with a marked draw check arrow while you shoot the way you actually shoot, which is why the shop number is authoritative and the wingspan formula is only a starting estimate.
How we choose: we compare published manufacturer specifications, verified owner reviews, and pro shop guidance. We do not test gear in person. Draw weight and arrow spine affect safety, so follow your bow manufacturer's specifications and have setup work checked by a qualified pro shop.