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Archer's Advantage Says

Arrow Spine Calculator

Convert between different spine measurement standards. ATA spine is measured as deflection in inches at a 28" span with an 880 gram (1.94 lb) load. Adjust the Load, Span, and Deflection values to calculate the equivalent ATA Spine.
Load
The weight applied to the center of the arrow shaft during spine testing. ATA standard is 880 grams (1.94 lbs).
Span
The distance between the two support points during spine testing. ATA standard is 28 inches (711.2 mm).
Deflection
The amount the shaft bends under load. This deflection value at ATA standard conditions equals the spine rating.
ATA Spine
0.500
About ATA Spine Measurement: The Archery Trade Association (ATA) standard for measuring arrow shaft spine uses a 28-inch span between support points and an 880-gram (1.94 lb) weight suspended from the center of the shaft. The deflection in inches under this load is the ATA spine rating. A lower spine number indicates a stiffer shaft. This calculator allows you to convert spine measurements taken with different loads, spans, or deflection units to the standard ATA spine rating.