What Is Draw Length?
Draw length is the distance, in inches, that an archer pulls the bowstring back to a consistent anchor point at full draw. It is one of the most important measurements in archery because a bow that is set up for the wrong draw length will feel awkward, hurt accuracy, and can even be unsafe. This calculator uses the popular "wingspan" method to give you a quick, reliable starting estimate.
How to Use This Calculator
Stand with your back to a wall and stretch both arms out horizontally, forming a "T". Have a friend measure from the tip of one middle finger to the tip of the other — this is your arm span (wingspan). Enter that number in inches and the calculator divides it by 2.5 to estimate your draw length. The result is also shown in centimeters for convenience.
The Formula Explained
The standard rule of thumb is:
$$\text{Draw Length (inches)} = \frac{\text{Arm Span (inches)}}{2.5}$$
This works because, for most people, arm span is roughly equal to height, and draw length scales proportionally with arm reach. The factor of \(2.5\) reflects the typical geometry of an archer at full draw with a proper anchor point.
Worked Example
Suppose your arm span measures 70 inches. Dividing by 2.5 gives $$70 \div 2.5 = 28 \text{ inches}.$$ So your estimated draw length is 28 inches, or about 71.12 cm. You would then choose arrows and set up a bow around a 28-inch draw length.
FAQ
Is this measurement exact? No — it's an estimate. For a precise figure, draw a measuring arrow on a bow and have a coach check your anchor point. The wingspan method is excellent for first-time setups.
Why divide by 2.5 and not another number? 2.5 is the long-standing industry rule of thumb that matches typical full-draw archer geometry across a wide range of body sizes.
What if my arm span and height differ a lot? The wingspan method follows your reach, which usually predicts draw length better than height. If they differ greatly, treat the result as a starting point and fine-tune on a bow.
