Crossbow bolt build: 12.22% FOC

A 100 grain point on a 12.0 GPI, 20 inch shaft gives 12.22% FOC (high foc) and a total arrow weight of 395 grains. Adjust any component to see the effect.

A 100 grain point on a 20 inch shaft at 12.0 GPI balances 12.44 inches from the nock throat, giving 12.22% front of center — high foc — at a total arrow weight of 395 grains. A short, heavy bolt — the short length makes FOC very sensitive to point weight.

Arrow build

Component weights in grains; shaft weight comes from GPI × length.

Shaft length (in)

Shaft GPI

Point / broadhead (gr)

Insert (gr)

Outsert / collar (gr)

Nock (gr)

Fletching, all vanes (gr)

Wrap (gr)

Draw weight (lb)

For grains per pound

Front of center

12.22%

High FOC — Popular for hunting: better arrow flight stability and forgiveness, with only a modest drop in trajectory.

How this was calculated

FOC = 100 × (A − L ÷ 2) ÷ L

L = 20.00 in (arrow length)

A = 12.44 in (balance point)

A − L ÷ 2 = 2.44 in forward of centre

FOC = 12.22%

Arrow weight

Shaft: 240.0 gr
Front end (point + insert + collar): 125.0 gr
Back end (nock + fletching + wrap): 30.0 gr
Total: 395.0 grains
6.58 grains per pound of draw weight

The balance point is estimated by treating the shaft as a uniform rod. Weigh and balance the finished arrow for an exact figure.

What the number means

FOC range	Description
under 7%	Low FOC — Flatter trajectory but less forgiving in flight. Common on target setups shooting light points.
7–10%	Normal FOC — The range most factory arrows land in. A good all-round balance of trajectory and stability.
10–15%	High FOC — Popular for hunting: better arrow flight stability and forgiveness, with only a modest drop in trajectory.
15–19%	Extreme FOC — Ashby-style setup. Strong penetration and stability; expect a noticeably more arcing trajectory past 30 yards.
19%+	Ultra-extreme FOC — Maximum penetration territory. Trajectory drops off quickly, and arrow tuning gets fussy.

This build in numbers

Shaft length	20 in
Shaft GPI	12.0 grains per inch
Shaft weight	240 gr
Point	100 gr
Insert	25 gr
Nock	12 gr
Fletching	18 gr
Total arrow weight	395 gr
Balance point	12.44 in from the nock throat
Front of center	12.22% (High FOC)

Popular for hunting: better arrow flight stability and forgiveness, with only a modest drop in trajectory.

Compare other builds

100 grain broadhead build The most common whitetail setup: a 100 grain head on a mid-weight shaft. 125 grain broadhead build Adding 25 grains up front is the cheapest way to lift FOC by roughly two points. 150 grain point build A brass insert plus a heavy head pushes this build into high FOC territory. 175 grain single-bevel build Heavy front end on a stout shaft — an Ashby-inspired penetration setup. 200 grain point build Extreme FOC for big game, at the cost of a noticeably arcing trajectory. Target arrow build Light shaft, small vanes and a field point — a flat-shooting target setup with normal FOC. Traditional arrow build Full-length shaft with feathers: heavier at the back, so FOC lands lower.

Frequently asked questions

What FOC does a 100 grain point give? ▾

On this build — a 20 inch shaft at 12.0 GPI with a 25 grain insert, 12 grain nock and 18 grains of fletching — a 100 grain point gives 12.22% FOC, which counts as high foc. Change any component in the calculator to see how the number moves.

How much does this arrow weigh? ▾

About 395 grains in total: 240 grains of shaft, 125 grains up front, and 30 grains at the back.

Is 12.22% a good FOC? ▾

High FOC. Popular for hunting: better arrow flight stability and forgiveness, with only a modest drop in trajectory.

Will this estimate match my measured FOC? ▾

It should be close. The estimate treats the shaft as a uniform rod and puts the front components right at the tip, so a build with a long outsert or an unusual shaft taper can differ by a few tenths of a percent. Balance the finished arrow for the exact figure.

About this Calculator