Archery Arrow Spine Calculator
Find the correct arrow spine stiffness for your bow based on draw weight, draw length, and arrowhead weight.
For recurve and compound bows.
Arrow spine refers to the stiffness of an arrow shaft — how much it flexes when shot. Getting the right spine is critical for accuracy. A spine that is too weak (too flexible) or too stiff will cause the arrow to fly erratically.
How spine is measured:
Arrow spine is measured by the AMO/ATA deflection method: A 28-inch arrow is supported at two points 26 inches apart, and a 1.94 lb (880g) weight is hung from the center. The deflection in inches × 1000 = the spine number.
Lower spine number = stiffer arrow
- 300 spine = very stiff (for heavy draw weights)
- 400 spine = medium stiff
- 500 spine = medium flex
- 600 spine = flexible (for light draw weights)
Common spine numbers:
| Spine | Draw Weight Range | Typical Use |
|---|---|---|
| 250–300 | 65–80 lbs | Heavy compound, hunting |
| 340–350 | 55–70 lbs | Mid-weight compound |
| 400 | 45–60 lbs | Standard compound / recurve |
| 500 | 35–50 lbs | Recurve, lighter compound |
| 600 | 25–40 lbs | Light recurve, youth bows |
| 700–900 | Under 30 lbs | Youth, beginner recurve |
Factors that require a stiffer (lower number) spine:
- Heavier arrowheads (100+ grains) — add ~25 spine points per 25 extra grains
- Longer arrows (above 28") — add spine stiffness for each extra inch
- Higher draw weight
- Shooting off-the-shelf recurve (more archer’s paradox flex needed)
Compound vs recurve:
- Compound bows: Use the actual peak draw weight for spine selection
- Recurve / traditional bows: Use the draw weight AT YOUR draw length (not the bow’s rated weight) Most recurve bows are rated at 28" draw — if you draw shorter or longer, adjust accordingly
Arrow length:
A properly fitted arrow should extend 1–2 inches past the rest when at full draw. Arrows that are too short are a safety hazard.
The “weak side” rule:
If in doubt, choose a slightly weaker spine (higher number) rather than too stiff. A slightly weak spine is more forgiving than a spine that is too stiff.