Calculate arrow FOC using Easton shaft GPI presets for FMJ, Axis, Carbon One, and Bloodline lines. Includes an Easton spine chart quick reference and KE comparison.
Pick your Easton shaft and enter build details. FOC calculates using the ATA/AMO formula.
FOC% = ((A − L/2) ÷ L) × 100
A = distance from nock throat to balance point; L = total shaft length.
| Model | GPI | Common Spine | Typical Use |
|---|---|---|---|
| Easton FMJ 5mm | 7.6–9.4 | 300–500 | Heavy hunting / penetration |
| Easton FMJ 4mm | 8.7–10.0 | 250–400 | Ultra-heavy hunting / dangerous game |
| Easton Axis 5mm | 8.1–9.0 | 300–500 | Small-diameter hunting |
| Easton Axis Match Grade | 9.0 | 300–400 | Match-grade target / hunting |
| Easton Carbon One | 6.2 | 400–600 | Light target / 3D |
| Easton Bloodline | 7.3 | 400–500 | Budget hunting |
| Easton Carbon Injexion | 9.0 | 250–400 | Deep-penetration hunting |
| Easton Hexx | 6.3 | 340–500 | Light hunting |
Source: Easton Archery published shaft specification guide (2024–2025).
FOC and kinetic energy measure different things. High FOC improves broadhead control and penetration potential; KE measures the total energy delivered at impact. Use both for a full picture.
Run your setup through the kinetic energy calculator after finalizing FOC.
Easton publishes shaft specifications and spine charts but does not maintain a standalone FOC tool. All legitimate FOC calculators use the same ATA/AMO formula — results should be identical when the same measurements are used.
Easton FMJ shafts combine a carbon core with a thin aluminum jacket. This gives higher mass per inch (heavier GPI) and a smaller diameter than pure aluminum, which increases FOC when paired with heavy front inserts.
Most 70 lb compounds at 29 in draw with a 100–125 gr point tune best with Easton 340 (FMJ, Axis). Heavy points or 30+ in draw can require 300. Confirm with our spine calculator.
Yes — FOC formula is universal. For crossbow speed and drop, use our crossbow ballistic calculator.
FMJ uses an aluminum jacket over a carbon core (heavier GPI, more momentum). Axis is pure carbon, small diameter, moderate GPI. FMJ typically produces higher FOC for the same insert due to higher shaft mass.