Draw Length Calculator
Estimate draw length from wingspan (AMO rule: wingspan ÷ 2.5).
How this works
This is the long-standing AMO (Archery Manufacturers Organization) rule of thumb: for most adults, arm span correlates closely enough with draw length to give a solid starting estimate before you ever touch a bow.
Measuring wingspan accurately
Stand with your back against a wall, arms stretched straight out to the sides at shoulder height, palms forward, and measure fingertip to fingertip. Getting this number right matters more than the formula itself — a half-inch error in wingspan becomes a real difference in draw length, which affects everything from arrow speed to your bow's let-off feel.
Frequently asked questions
How accurate is the wingspan-divided-by-2.5 rule?
It gets most adults within about half an inch of their true draw length, which makes it a solid starting estimate — but a bow shop's draw-length check on an adjustable-module bow is the real confirmation.
What's the right way to measure my wingspan?
Stand with your back against a wall, arms stretched straight out to the sides at shoulder height, palms forward, and measure fingertip to fingertip — getting this measurement right matters more than the formula itself.
Does draw length change as I get more flexible or stronger?
It can shift slightly with changes in stance, shoulder mobility, or anchor point technique, which is one more reason a periodic in-person check at a bow shop is worth doing even after you've found your starting number here.
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