The best way is to do an F.O.C. analysis. It is a simple analysis that requires no special equipment. My advice would be to start with a 100 gr Broadhead and check your F.O.C. Then check it with a 125 gr. The calculations for my arrows follow and I shoot 100 gr Thunderheads since mechanicals are illegal in Washington State.

FRONT OF CENTER %

Arrows with a weight forward balance between 7% and 10% are the most aerodynamic.

To find your F.O.C. %

1. Measure the arrow shaft from the tip of the broadhead to the end of the nock. Divide this measurement by 2 to find the center point (i.e. 30” shaft divided by 2 = 15).
2. Mark the center point with a felt tip marker. Now balance the arrow.
3. Mark the balance point with a felt tip marker. Divide the distance between the two marks by the overall length of the arrow then multiply the result by 100. (i.e. distance between the two marks of 30’ shaft is 2.5” then 2.5 divided by30 times 100=8.33%)

When greater than 10% use a lighter broadhead
When less than 7% use a heavier broadhead.


My hunting shaft F.O.C. calculations.
Over all length: 30 7/16”
Mid Point: 30.44 / 2 =15.22” (15 7/32”)
Difference between mid point and balance point: 2.31” (2 5/16”)

Therefore F.O.C. = (2.31/30.44) X 100 = 7.59%

Since 7.59 is > 7% but < 10% my F.O.C. is acceptable and aerodynamic.