Archery Arrow Spine Calculator
Find the recommended arrow spine, arrow weight, and front-of-center percentage for your bow setup.
How to Use the Archery Arrow Spine Calculator
- Enter your bow's draw weight in pounds.
- Enter your arrow length in inches.
- Enter the point weight in grains.
- Select bow type: recurve or compound.
- Click Calculate to see recommended spine, arrow weight, and FOC.
Use Cases
- •Selecting arrows when setting up a new bow.
- •Tuning arrow flight for improved accuracy.
- •Understanding the relationship between equipment parameters and arrow behavior.
Formula
Formula: Adjusted draw weight accounts for bow type (compound ×0.75) and length/point corrections. Spine ≈ 1000 / adjusted weight. Arrow weight = shaft (6 gr/in) + point weight. FOC = front weight contribution as % of total.
Frequently Asked Questions
What is arrow spine?
Arrow spine is the stiffness of an arrow shaft, measured as deflection in thousandths of an inch under a 1.94 lb load. A lower spine number means a stiffer arrow. Matching spine to your draw weight is critical for accuracy.
What is FOC (front-of-center)?
FOC is the percentage of the arrow's total length that the balance point sits in front of the arrow's center. A higher FOC (10–15%) improves flight stability and penetration.
Why do compound bows need lighter spine than recurve?
Compound bows release from full draw via let-off, producing a less severe paradox (arrow bend) at release. This allows a stiffer (lower number) spine compared to recurve or traditional bows.