Planning arrows for a recurve or longbow? A calculator can help you compare a setup, but its answer is not a guarantee that a shaft will suit your bow and shooting style. ## Start with a build record Write down your bow model, draw length and draw weight at your draw length, plus the shaft model, shaft length and component weights you intend to use. Distinguish measured values from markings or estimates. Follow the shaft manufacturer's measurement conventions and selection chart for that exact shaft. ## Compare the build on BowStrike [Open the BowStrike Arrow Builder](/arrow-builder.html) to compare total arrow weight and estimated front-of-center balance as you change components. Its spine comparison is a simplified chart-based starting point, not a complete dynamic-spine simulation. Insert weight contributes to its total weight and FOC estimate, but is not an input to its spine recommendation. Weigh and measure the finished arrow to check the estimates. ## Use another reference, not a verdict The [3Rivers dynamic-spine calculator](https://www.3riversarchery.com/dynamic-spine-arrow-calculator-from-3rivers-archery.html) is another reference for traditional setups. 3Rivers cautions that real-world results vary and recommends testing shafts before buying a full set. Its model and BowStrike's simplified comparison are different; matching numbers are not proof of suitability, and disagreement is a reason to check the inputs and ask a qualified shop. Before purchasing, cutting or shooting, check the shaft manufacturer's current chart and instructions, and have a qualified archery shop help confirm the setup. Use appropriately selected test shafts under those instructions before committing to a full set. A calculator cannot inspect equipment or certify an arrow as safe; do not keep shooting damaged or questionable arrows. **Discussion:** What bow and arrow combination are you comparing? Share the setup details, manufacturer chart and what you have actually measured so others can understand the question. Original BowStrike educational note. Source checked October 26, 2026: [3Rivers Archery](https://www.3riversarchery.com/dynamic-spine-arrow-calculator-from-3rivers-archery.html). This is not a hands-on review, product endorsement or universal tuning prescription.