Draw Length Calculator

Arm Span (Wingspan)

Unit

What is a Draw Length Calculator?

A draw length calculator is a tool used by archers to estimate the optimal distance they should pull back the bowstring. This measurement is crucial for selecting a bow that fits your body, which in turn improves accuracy and comfort. Draw length is formally defined by the Archery Trade Association (ATA) as the distance from the nocking point on the string to the pivot point of the grip, plus 1 3/4 inches.

Draw Length Formula and Explanation

The most common and reliable method for estimating draw length is the arm span method. This method uses your wingspan to calculate your draw length. The formula is as follows:

Draw Length = Arm Span / 2.5

Variables for Draw Length Calculation
Variable	Meaning	Unit	Typical Range
Arm Span	The distance from the tip of one middle finger to the other when your arms are stretched out to the sides.	Inches or Centimeters	60-80 inches (152-203 cm)
Draw Length	The calculated optimal distance to pull back the bowstring.	Inches	24-32 inches

Practical Examples

Here are a couple of examples to illustrate how the draw length calculator works:

Example 1:

Input (Arm Span): 70 inches
Calculation: 70 / 2.5 = 28
Result (Draw Length): 28 inches

Example 2:

Input (Arm Span): 180 cm
Calculation: (180 / 2.54) / 2.5 = 28.3
Result (Draw Length): 28.3 inches

How to Use This Draw Length Calculator

Measure your arm span by extending your arms out to your sides and having someone measure from the tip of one middle finger to the other.
Enter your arm span measurement into the “Arm Span” field.
Select the unit of measurement you used (inches or centimeters).
Click the “Calculate” button to see your estimated draw length.
The result will be displayed in inches, as this is the standard unit for draw length in archery.

Key Factors That Affect Draw Length

Body Size: Your height and arm length are the primary factors that determine your draw length.
Shooting Form: Your posture and anchor point can slightly alter your ideal draw length.
Bow Type: Different types of bows (recurve, compound, longbow) may require slight adjustments to your draw length.
Anchor Point: The point on your face where you consistently draw the bowstring to will influence your draw length.
Release Style: The type of release aid you use can also have a minor effect on your optimal draw length.
Flexibility: Your shoulder and back flexibility can impact your ability to achieve a full and proper draw.

FAQ

How do I measure my arm span accurately?

Stand with your arms stretched out to the sides, forming a “T” shape with your body. Have a friend measure the distance from the tip of one middle finger to the other.

What if I don’t have anyone to help me measure my arm span?

You can stand with your back against a wall, extend one arm, and mark the tip of your middle finger. Then, do the same with the other arm and measure the distance between the two marks.

Why is my draw length important?

Your draw length is crucial for selecting the right size bow and arrows, ensuring proper shooting form, and maximizing your accuracy and consistency.

Can my draw length change over time?

Yes, your draw length can change slightly as you grow, or as your shooting form and flexibility improve.

What is the difference between ATA and AMO draw length?

The Archery Trade Association (ATA) has standardized the measurement of draw length. AMO (Archery Manufacturers and Merchants Organization) was the previous name for the ATA. The terms are often used interchangeably.

What if my calculated draw length is between sizes?

It’s generally better to choose a slightly shorter draw length than one that is too long, as it is easier to manage.

How does draw length affect draw weight?

For recurve bows, the draw weight increases the further you pull back the string. For compound bows, the draw weight is determined by the cam system and is less affected by small variations in draw length.

What if I am still unsure about my draw length?

It’s always best to visit a local archery pro shop for a professional fitting. They can measure you accurately and help you find the perfect bow setup.