Easton Arrow Spine Calculator
Use this tool to estimate a starting spine size for Easton shafts. Enter your setup details, then fine-tune with paper tuning and bare shaft testing.
Picking the right arrow spine can make your bow feel easier to tune, produce better broadhead flight, and tighten groups at distance. If you shoot Easton shafts, this calculator gives you a practical first recommendation in common spine classes such as 600, 500, 400, 340, or 300.
What “spine” means in plain language
Static spine
Static spine is the measured stiffness of an arrow shaft. In carbon sizing, a lower number is stiffer. For example, a 300 spine is stiffer than a 400 spine.
Dynamic spine
Dynamic spine is how stiff the arrow behaves when actually shot. Arrow length, point weight, release style, and cam aggression can all make the same shaft act weaker or stiffer in real-world shooting.
How this easton spine calculator estimates your result
This tool starts from your draw weight and then applies adjustments for setup factors that change dynamic spine. It then maps the adjusted value to a common Easton spine class.
- Longer arrow = weaker reaction, often needs stiffer spine.
- Heavier point = weaker reaction, often needs stiffer spine.
- Aggressive cam = stronger launch, often needs stiffer spine.
- Finger release / traditional setups are shifted toward weaker recommendations compared with a modern mechanical release baseline.
Quick reference spine zones
| Effective Setup Weight (lb) | Typical Starting Spine |
|---|---|
| Up to 30 | 1000 |
| 31–35 | 900 |
| 36–40 | 800 |
| 41–45 | 700 |
| 46–50 | 600 |
| 51–55 | 500 |
| 56–60 | 400 |
| 61–67 | 340 |
| 68–74 | 300 |
| 75+ | 250 |
How to use your result
1) Buy close, then tune
If the calculator outputs 400, many archers also test neighboring sizes (500 and 340) when they are near a boundary. Small changes in insert weight, nock fit, rest position, or fletching can affect final choice.
2) Verify with a tune process
- Paper tune at short distance
- Bare shaft check at 15–20 yards
- Broadhead-to-field-point comparison (hunters)
3) Keep total arrow build in mind
Spine is only one part of the build. Total arrow weight, FOC, vane profile, and intended use (3D, indoor, hunting, outdoor target) all matter.
Common mistakes to avoid
- Choosing spine only by draw weight and ignoring arrow length.
- Switching from 100-grain to 150-grain heads without rechecking spine.
- Assuming all bows with the same poundage need the same shaft.
- Skipping final tuning after buying arrows.
FAQ
Is a lower spine number stiffer?
Yes. A 300 spine is stiffer than a 400 spine.
Should I pick the stiffer option for broadheads?
Often yes if you are between sizes, especially on fast compound setups. But verify with tuning and broadhead flight.
Can this replace Easton’s official selector?
No. Use this as a starting estimate, then confirm with official manufacturer guidance and real shooting tests.