FOC (Front of Center) is very important to bowhunters and target archers as well. Having a proper FOC will help increase arrow stability, accuracy and penetration.  IMHO 12% is bare minimum. 17 to 20% will work really good and greatly enhance penetration.
Measure from the throat of the nock to the end of the shaft. If you want to include the length of the point, go ahead. Remember you must use the same measurements when making a comparison..

Enter the total length “L”:

Enter the measured length “B”:

FOC = %