Arrow spine calculator
Chart lookup only — we do not extrapolate beyond published manufacturer tables.
Calculator
Recommended spine: 500
From Recurve / barebow carbon shaft selection (indicative) (Easton), chart dated 2024-01-15. View source chart
This is a starting recommendation, not a guarantee. Always inspect carbon arrows for cracks before shooting, and make sure arrows are long enough to clear the riser at full draw. Ask a coach or a bow shop to confirm spine for high draw weights.
How it works
Static spine (ASTM F2031): an 880 g (1.94 lb) weight hangs from the centre of a 28 in span; spine number = deflection in inches × 1000. Lower spine number = stiffer arrow.
Manufacturers publish selection charts because dynamic spine also depends on bow, point weight, and tune — there is no single validated formula.
Formula
This tool uses chart lookup only. We match your inputs to transcribed rows in spine_charts.json and never invent a spine outside chart coverage.
Worked example
A recurve archer at 32 lb, 28 in arrow, 100 gr point on carbon — if the chart has a matching cell, we show that spine value; otherwise we tell you to use the manufacturer chart directly.
FAQ
Can I convert old GNAS spine? No — older systems used different weights and spans.
What next? Paper-tune or walk-back with a coach or shop to confirm before shooting at full draw weight.