Arrow FOC Calculator

FOC is how far forward of the middle an arrow balances, written as a percentage of its length. Balance the finished arrow on a knife edge, enter the length from the nock throat and where it balanced, and this returns the ATA figure along with how far ahead of centre that is. A second form estimates the same thing from a parts list, and will tell you what point weight would reach an FOC you are aiming for. That form assumes the point sits at the very tip and the fletching at the very back, so a measured arrow is always the better answer.

Calculator Type

Balance the finished arrow on a knife edge or the back of a ruler, then measure from the throat of the nock to that point.

Arrow Length (inches) *

Throat of the nock to the end of the shaft. The point is not part of this measurement.

Balance Point (inches from the nock throat) *

Total Arrow Weight (grains, optional)

Peak Draw Weight (lb, optional)

Only used to work out grains per pound.

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No finished arrow needed. Add up what you plan to build and this estimates where it will balance.

Arrow Length (inches) *

Throat of the nock to the end of the shaft, the point left out.

Shaft Weight (grains per inch) *

Printed on the shaft or in the maker's chart. Carbon hunting shafts run roughly 7 to 12 gpi.

Point or Broadhead (grains) *

Insert, Outsert or Collar (grains)

Nock (grains)

Fletching, All Vanes Together (grains)

Three 2 in vanes come to roughly 15 to 24 grains with the glue.

Wrap (grains)

Peak Draw Weight (lb, optional)

FOC You Are Aiming For (%, optional)

Fill this in and the result says what point weight would get you there.

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