Draw Length Calculator (archery draw length from arm span)

Understanding the draw length calculator — concept and principle

Draw length is how far you pull the bowstring back at full draw. A bow set to the wrong draw length is uncomfortable, less accurate and can be unsafe. This calculator gives a quick starting estimate from your arm span using the common "span ÷ 2.5" rule, in inches and centimetres, rounded to the nearest half inch.

How it is calculated

Draw length (in) ≈ arm span (in) ÷ 2.5

• Arm span is measured fingertip to fingertip with your arms straight out in a "T", palms forward.
• Centimetres are converted with 1 in = 2.54 cm.
• Bows are specified in inches, so the result is also rounded to the nearest half inch.

The principle

Draw length depends on body proportions: longer arms and broader shoulders mean a longer pull. Arm span is easy to measure and closely tracks those proportions, so dividing it by a fixed factor gives a practical first estimate. The Archery Trade Association's Archery 360 programme recommends this method as a starting point. For compound bows, draw length is defined as the distance from the nocking point to the deepest part of the grip plus 1¾ inches, which is how manufacturers specify their bows.

Worked example

Default input: arm span 178 cm.

1. Arm span in inches = 178 ÷ 2.54 = 70.1 in.
2. Draw length = 70.08 ÷ 2.5 = 28 in (28.03).
3. In centimetres: 28.03 × 2.54 = 71.2 cm.
4. Rounded to the nearest half inch = 28 in.

How to read the result

Use the number to choose a bow or an adjustable compound setting, then have a bow shop or coach check it at full draw. Signs that draw length is too long include the bow arm locking straight or the string hitting your forearm; too short can feel cramped and give inconsistent anchors. Recurve archers' actual draw also depends on anchor point and form.

Common mistakes

• Measuring arm span with hunched shoulders or bent elbows.
• Measuring to the wrist instead of the fingertip.
• Treating the estimate as final without checking at full draw.
• Confusing draw length with arrow length; arrows are usually cut a little longer.

Frequently asked questions

How do I measure arm span alone?

Stand against a wall with arms out and mark each fingertip, then measure between the marks.

Is draw length the same as arrow length?

No. Arrows are normally a little longer than draw length for safety.

Does draw length change with bow type?

Your body sets the base, but form and bow design make small differences.

What if I am between half inches?

Try both on a bow and choose the one that feels steady at full draw.

Sources: Archery 360 (Archery Trade Association), "Archery Lingo: Draw Length" and "Nerd Out with Archery Math" (2021)