Arrow Metrix Logo

ARROW METRIX

Professional Spine Calculator v3.0

Base Setup

Leave blank if unknown

Fine-Tune
Adjustments
0gr
0"
0lb
Results
Exact Spine
---

Configuration

Reference table:---
Draw Weight:---
Arrow Length:---
Tip Weight:---
Adjusted Weight:---
F.O.C. Calculator

Front of Center Balance

FOC Results

Shaft Weight:---
Total Vane Weight:---
Total Arrow Weight:---
Balance Point:---
F.O.C. Percentage
---%

Optimal FOC: 7% - 15%

Kinetic Energy

Arrow Power & Penetration

Arrow weight:--- gr

Calculated from tip, length, GPI, nock & vanes — or override below

Measured or estimated

Kinetic Energy
--- ft-lb

Enter weight & speed

Performance

Kinetic Energy:---
Momentum:---
KE Guidelines
65+ ft-lb - Large game
50-65 ft-lb - Med/Large
40-50 ft-lb - Medium
25-40 ft-lb - Small game
<25 ft-lb - Target only
FPS Estimator

Uses Base Setup, Results & FOC

IBO:---
Draw weight:---
Arrow length:---
Arrow weight:---

From KE column — or override below

Estimated Speed
--- fps
Likely range:---
Base Arrow Setup

Leave blank if unknown

Results
Exact Interpolated Spine
---

Configuration Summary

Reference table:---
Effective Draw Weight:---
Effective Arrow Length:---
Effective Tip Weight:---
Adjusted Bow Weight:---

Fine-Tune Parameters

Adjust values to experiment

0gr
0"
0lb
F.O.C. Calculator

Front of Center Balance

FOC Results

Shaft Weight:---
Total Vane Weight:---
Total Arrow Weight:---
Balance Point:---
F.O.C. Percentage
---%

Optimal FOC: 7% - 15%

Kinetic Energy
Arrow weight:--- gr

Calculated or override below

Measured or estimated

KE & Momentum

Kinetic Energy:---
Momentum:---
Kinetic Energy
--- ft-lb

Enter weight & speed

FPS Estimator

Arrow weight from KE column

IBO:---
Draw weight:---
Arrow length:---
Arrow weight:---
Estimated Speed
--- fps
Likely range:---
How To Use Arrow Metrix

1. Choose Compound or Recurve, then enter your draw weight (lb), arrow length (in), and tip weight with insert (gr). For compound bows, add IBO speed if you know it.

2. Fine Tuner: Enter your data in the Base Setup, then use the tuner sliders to make adjustments and find a real spine and a good solution for your arrow build.

3. FOC Calculator: Enter shaft GPI, nock weight, vane weight, and vane count to see your Front of Center %.

4. Kinetic Energy: Enter total arrow weight and speed to calculate KE and momentum.

How To Measure Arrow Length

Arrow length is measured from the throat of the nock (the deepest part where the string sits) to the end of the shaft (back of the point, NOT including the point itself).

To measure: Place your arrow on a flat surface. Measure from the nock throat groove to where the insert or point begins.

What Is IBO Speed?

IBO stands for International Bowhunting Organization. IBO speed is measured under: 70 lb draw, 30" draw length, 350 grain arrow.

Higher IBO speeds generally require stiffer arrow spines. Enter your bow's IBO rating (from specs) to fine-tune recommendations. Leave blank if unknown.

F.O.C. Ranges Explained

7% - 12% FOC: Ideal for target. Flat trajectory, forgiving flight.

12% - 15% FOC: Balanced for hunting. Good penetration.

15% - 19% FOC: High FOC. Excellent penetration.

19%+ FOC: Extreme FOC. Max penetration, precise tuning needed.