DO-A // BALLISTIC_LAB // v.2026

BALLISTIC_F.O.C._LAB

Arrow FOC Diagram
50% CENTER
BALANCE POINT

1. SHAFT & SPEED

IN
GN
FPS

Check this to simulate FPS loss as you add weight (-1 FPS per 3gn).

2. FRONT END WEIGHT

GN
GN

3. REAR END WEIGHT

GN
GN
PCS
GN
TOTAL WEIGHT
0 GN
EFFECTIVE VELOCITY
0 FPS
SIMULATED F.O.C.
0.00%
KINETIC ENERGY
0 FT-LBS
MOMENTUM
0 SLUG-FPS
KINETIC REFERENCE CHART (EST)
SMALL GAME
MEDIUM GAME
LARGE GAME
DANGEROUS
ⓘ

Calculated values are theoretical. Real-world lethality is determined by shot placement and broadhead efficiency. User assumes all responsibility.

© 2026 DO-A ARCHERY. BALLISTIC LAB v1.0

04. DEFINITION

FOC (Front of Center) is the percentage of the arrow's total weight located in the front half of the shaft. It is the primary driver of down-range accuracy and penetration potential.

Adding weight to the tip pulls the balance forward (raising FOC). Adding weight to the back pulls it backward (lowering FOC). Precision builds typically fall within the 7% to 15% window.

05. THE ALGORITHM

$$FOC \% = \left[ \frac{L_{bal} - (L_{tot}/2)}{L_{tot}} \right] \times 100$$
$$L_{bal}$$ = Balance Point Location  |  $$L_{tot}$$ = Total Arrow Length

06. PHYSICAL VALIDATION PROTOCOL

01 MEASURE LENGTH

Measure the total arrow length from the throat of the nock to the end of the shaft (or point tip, depending on method preference).

02 LOCATE BALANCE

Place the arrow on a thin edge (a knife edge or ruler). Find the exact point where the arrow hovers level. Mark this spot.

03 RECORD DATA

Measure the distance from the throat of the nock to your balance mark. This is your Center of Gravity (COG).

04 CALCULATE

Input your Total Length and Balance Point into the formula above to verify results.