Estimate an archery draw length from measured wingspan, calculate a traditional bow’s weight at another draw length, or reverse-solve its marked draw weight.
Draw Length and Traditional-Bow Weight Methods
The wingspan method is a fit starting point, while the draw-weight relationship is a user-controlled linear estimate for recurves and longbows. Compound cam systems do not follow the same pounds-per-inch behavior.
How the Calculation Works
Each solve mode shows only its required source values. Irrelevant fields leave the active form and their values are preserved when you switch back.
How to Use This Calculator
- Select the value or workflow you want in the Solve for menu.
- Enter only the visible source values and use the units shown beside them.
- Select Calculate and review the primary answer, supporting values, warning, and steps.
- Use Reset before starting a different bow, arrow, or round.
Worked Example
A 70-inch wingspan estimates a 28.00-inch draw length. Separately, a bow marked 40 lbf at 28 inches with a chosen 2.5 lbf/in gain estimates 43.75 lbf at 29.5 inches.
Input and Result Guide
| Item | How to use it |
|---|---|
| Wingspan | Measure fingertip to fingertip with arms extended naturally. |
| Marked values | Read both the weight and reference draw length printed on the bow. |
| Gain per inch | Use a measured value when possible; 2.0 to 3.0 lbf/in is only a planning range. |
| Draw length result | Treat wingspan divided by 2.5 as a starting estimate to be fitted and measured. |
Interpreting the Result
Use the draw-length estimate to start a fitting conversation and the weight estimate to compare a traditional bow at a different draw. Confirm both on the actual setup before selecting arrows.
Assumptions and Limitations
Body proportions, posture, anchor point, release style, limb design, and stacking can change the result. The weight relationship is not valid for compound bows, and no estimate replaces an ATA draw-length measurement or bow scale.
Common Questions
Why did a field disappear after I changed Solve for?
A hidden field is either the requested output or irrelevant to the selected workflow. Enter the remaining visible source values.
Will my last successful calculation be restored?
Yes. The calculator saves the last successful source inputs in this browser and recomputes the result when restored. Reset clears that saved state.
Sources
Archery Trade Association, Technical Guidelines; Bear Archery, draw-length fitting guidance; bow manufacturer’s marked specifications.