ARROW WEIGHT AND FOC (FORWARD OF CENTER)
FOC is the acronym for Front of Center. It refers to how far the center of gravity is in front of the center of the arrow length. It is shown as a percentage. The more weight towards the tip of the arrow the higher the FOC. The more weight towards the back of the arrow the smaller the FOC. A properly balanced arrow has an FOC of 7% to 15%.
Enter the information below to calculate your arrow weight and FOC. Enter 0 if your arrows do not include an item in the list.
Manual FOC Calculation
The AMO-Standard F.O.C. balance formula is: %FOC = (100x(A-L/2))/L
For those of you who prefer to calculate your FOC the old way with a calculator, this is for you:
A = Balance point as measured from the throat of the nock to the point of balance. L = Total arrow length as measured from the throat of the nock to the back of the point. (Do not include the length of the point in this measurement.)
1. Measure the arrow length from the throat of the nock to the end of the shaft. (Back of the point) e.g. 28.5"
2. Divide the total length number by two (2). (Or multiply it by 0.5.) e.g. 28.5/2 = 14.25 or 28.5 x 0.5 = 14.25
3. Find the arrow's balance point. Measured from the nock throat to the balance point. e.g. 19.0"
4. Subtract half the total length from the balance point number. e.g. 19.0" - 14.25" = 4.75"
5. Multiply that result by 100. e.g. 4.75 x 100 = 475
6. Now divide that number by the total arrow length. e.g. 475 / 28.5 = 16.6% FOC
Example: A 28.50” (BOP) arrow has a balance point of 19.00”.
Half of the total arrow length is 14.25.
Subtract 14.25 from the 19" and you get 4.75".
Multiply that by 100 = 475.
Now divide 475 by the total length which is 28.5 = 16.6.
Your FOC measurement is 16.6%
Enter the arrow weight and velocity to calculate the kinetic energy of your current bow and arrow setup.
ARROW WEIGHT -> KINETIC ENERGY
Enter the following to generate the kinetic energy at different arrow weights.
|Arrow Weight (grains)||Velocity (fps)||Kinetic Energy (ft-lbs)||Site Tapes|
DRAW WEIGHT -> KINETIC ENERGY
Enter the following to calculate the kinetic energy at different draw weights.
|Draw Weight (pounds)||Velocity (fps)||Kinetic Energy (ft-lbs)||Site Tapes|