Arrow build calculator
Enter your arrow components once and get every key build metric simultaneously — total weight, FOC, grains per pound, kinetic energy, momentum, spine adjustment flag, and a purpose-matched build score. No switching between calculators.
Part of the Archery Calculators toolkit. If you need to look up individual metrics in isolation, use the dedicated FOC Calculator, Arrow Weight Calculator, or Kinetic Energy Calculator. This page optimises all of them together.
Arrow build optimiser
Fill in your components below. All metrics update live as you type. Inputs marked * are required for a complete result — optional inputs improve accuracy.
All metrics update live as you type.
What each metric means for your build
An arrow build is a system — every component affects every metric. Understanding the relationships lets you make intentional trade-offs rather than optimising one number at the expense of others.
Total arrow weight
The sum of all components in grains. Heavier arrows fly slower from the same bow but carry more momentum at any given speed. The minimum safe total is 5 grains per pound of draw weight (the ATA safety floor). Most hunting builds run 400–600 grains depending on draw weight and game species. Target builds run 280–380 grains for maximum speed and flat trajectory.
FOC (Front of Center)
The percentage of arrow length by which the balance point sits ahead of the arrow's physical centre. Low FOC (under 7%) produces unstable flight. Target FOC (7–11%) maximises accuracy at distance. Hunting FOC (11–19%) maximises penetration. EFOC (19%+) maximises penetration through bone. FOC is controlled by adjusting front-end weight (point and insert) relative to the rest of the build.
GPP (Grains Per Pound)
Total arrow weight divided by bow draw weight. The ATA minimum safe GPP is 5.0 — below this, excess energy is returned to the bow limbs and strings, risking damage and injury. For hunting, 6–8 GPP balances speed and penetration. 8–10 GPP is a heavy hunting build. The GPP check is bow-safety critical — always verify this before shooting a new build.
Kinetic Energy (KE)
Kinetic energy (ft-lbs) = ½ × mass × velocity². KE is the most commonly referenced metric for hunting suitability: 25 ft-lbs minimum for small game, 40 ft-lbs for deer, 50 ft-lbs for elk. KE rises steeply with speed — a 10% speed increase raises KE by 21%. However, KE alone does not predict penetration; momentum is equally important and decays more slowly through tissue.
Momentum
Momentum (slug·ft/s) = mass × velocity. Unlike KE, momentum is directly proportional to both mass and velocity — doubling mass doubles momentum. Momentum predicts continued penetration through tissue better than KE alone because it represents the arrow's resistance to deceleration. For a fixed bow, a heavier arrow produces more momentum than a lighter arrow despite flying slower, because the mass increase outweighs the speed decrease.
Spine adjustment flag
Heavy front-end weight (point + insert above 115 grains combined) makes the arrow behave as if it has weaker spine than its rating. The calculator estimates how many spine groups you may need to correct based on your front-end weight relative to a standard 100-grain point + 15-grain insert reference. A flag here means you should re-verify your spine selection — it does not mean the build is wrong, only that the spine needs to account for the front weight.
Optimal build targets by purpose
The right balance of metrics depends entirely on what you are building for. These are the evidence-based target ranges used by the build score in the calculator above.
| Purpose | FOC target | Total weight | GPP | KE minimum |
|---|---|---|---|---|
| Indoor target | 7–10% | 280–360 gr | 5–6.5 | — |
| Outdoor target / field | 7–11% | 300–420 gr | 5–7 | — |
| 3D archery | 8–12% | 320–420 gr | 5.5–7 | — |
| Turkey / light game | 10–14% | 350–450 gr | 6–7.5 | 25 ft-lbs |
| Whitetail / mule deer | 10–15% | 400–500 gr | 6–8 | 40 ft-lbs |
| Elk / black bear | 13–19% | 450–600 gr | 7–10 | 50 ft-lbs |
| Dangerous game / EFOC | 19%+ | 550–800 gr | 8–12 | 65 ft-lbs |
| Traditional archery | 11–15% | 400–600 gr | 7–11 | varies |
3D archery arrow setup
The 3D row in the table above reflects a different optimisation priority from hunting builds. In 3D archery, you are shooting at foam animal targets at unmarked distances — you estimate or range the target, then aim at the scoring ring. A faster, flatter-shooting arrow is the primary goal because it reduces the trajectory error introduced by any distance estimation mistake. Missing your distance estimate by 3 yards matters far less with a 300 fps arrow than with a 260 fps arrow.
What the 3D build score optimises for: The build score for 3D archery weights speed and trajectory flatness over penetration and momentum. GPP at the lower end of the safe range (5.5–7) is acceptable — the lighter arrow flies faster and flatter, which is the priority. FOC in the 8–12% range is sufficient for stable field point flight at 3D distances (typically 5–50 yards) without the higher FOC that broadhead-tipped hunting arrows need for steering correction.
Practical 3D arrow setup guidelines:
- Point weight: 75–100 grains. Lighter points reduce total weight and raise speed. Most 3D shooters use 100 grains for consistent feel; open-class competitors sometimes use 75 grains for maximum speed.
- Insert: Standard aluminium insert (12–16 grains). Heavy inserts raise FOC unnecessarily for a field point application and add weight that reduces speed.
- Shaft: A mid-weight carbon shaft at correct spine for your draw weight. Small-diameter shafts (4mm micro) are popular in open-class 3D for reduced wind drift and lower chance of destroying arrows that land close together on the target.
- Vanes: Small, low-profile vanes — 1.75″ to 2″ with minimal or zero helical. Less drag means higher speed and flatter trajectory. No broadheads in 3D means the steering correction requirement is lower than a hunting build. See the Arrow Fletching Guide for vane selection matched to field point use at 3D distances.
- Nock: Standard press-fit nock. Lighted nocks add rear weight that reduces FOC and speed — use only if course rules permit and the tracking benefit justifies the trade-off.
How changing one component affects everything else
The most common build mistake is changing one component to improve one metric without realising the knock-on effects. The calculator catches these automatically — but understanding the relationships makes intentional optimisation much faster.
Components for a custom arrow build
Every number in the calculator above corresponds to a physical component. These are the main variables you can change to hit your target metrics:
Carbon arrow
shafts —
shaft GPI is the primary weight and spine variable. Changing shaft model changes both shaft
weight and spine in one step. Match GPI to your target total weight before ordering.
Field points —
the most accessible way to adjust total weight and FOC. Available in 75–200 gr
increments. Build and verify with field points before switching to broadheads.
Heavy brass inserts —
the most efficient lever for raising FOC without affecting speed significantly. A
50-grain brass insert raises FOC by 2–4 percentage points on most builds compared to a
15-grain aluminium insert at the same point weight.
Nocks —
standard press-fit nocks are the lightest option (8–12 gr). Switch to lighted nocks
only if you accept the FOC reduction — always re-check the build calculator after
switching.
Vanes and fletching
—
vane weight sits at the rear of the arrow and reduces FOC. Minimise vane weight for
target builds; use larger, heavier vanes only where broadhead stability requires it.
Grain scale —
essential for accurate build calculation. Weigh each component individually before
building rather than relying on catalogue specifications, which are nominal not actual
weights.
Arrow build calculator — frequently asked questions
What is the best arrow build for deer hunting?
For whitetail deer, target 400–500 grains total weight, 10–15% FOC, 6–8 GPP, and at least 40 ft-lbs kinetic energy. A 27–29″ carbon shaft with a 100–125 grain broadhead and a 20–30 grain brass insert typically hits these targets. Enter your specific components in the build calculator above to verify all metrics against the deer hunting build score — components vary enough between manufacturers that nominal specs alone are not reliable for a tight build.
How does arrow weight affect FOC?
FOC is determined by where on the shaft the weight is distributed, not by total weight alone. Adding weight to the front (heavier point or heavier insert) raises FOC. Adding weight to the back (heavier nock, larger vanes) lowers FOC. Adding weight to the shaft adds to the middle, which also lowers FOC relative to a front-loaded build of the same total weight. The insert is the most efficient single lever for raising FOC because it sits at the very tip of the shaft where it has maximum leverage in the FOC calculation.
What does GPP mean and why does it matter?
Grains per pound (GPP) is total arrow weight divided by draw weight. Below 5.0 GPP, the bow has insufficient mass in the arrow to absorb the energy of the limbs returning, which transfers that energy back into the bow's structure, strings, and cables — risking damage and injury. This is the ATA's minimum safe standard. Most bow manufacturers specify a minimum arrow weight in their user manuals for the same reason. Always verify GPP before shooting a new build.
When should I use a heavy brass insert?
Use a heavy brass or stainless insert (25–100+ grains) when you want to increase FOC without significantly increasing total arrow weight or reducing speed. Compared to adding the same grain count via a heavier point, a heavier insert raises FOC more efficiently because the insert sits directly behind the point at the tip — maximum leverage position. A 50-grain brass insert raises FOC by approximately 2–4 percentage points on most carbon shaft builds compared to a standard 15-grain aluminium insert at the same point weight.
Does my arrow spine need to change if I increase point weight?
Yes — every 25 grains of front-end weight above the reference (typically 100-grain point + 15-grain insert = 115 grains combined) effectively weakens the arrow's spine by approximately one spine group. If you increase from a 100-grain to a 200-grain point, your 400-spine arrow may need to be replaced with a 350-spine or 300-spine arrow to maintain correct flex characteristics. The build calculator flags this when your front weight exceeds the reference threshold. Use the Arrow Spine Calculator to select the correct spine for your updated build, then paper-tune to confirm.
What is EFOC and when should I use it?
EFOC (Extreme Front of Center) means FOC above 19%, achieved by using very heavy inserts (50–150+ grains) combined with heavy points (150–300 grains). EFOC builds maximise penetration through bone and heavy tissue — research by Dr. Ed Ashby found meaningful penetration advantages over standard FOC builds on large, dangerous game. EFOC is appropriate for close-range dangerous game hunting and some traditional archery applications. The trade-off is a steep trajectory beyond 30–40 yards — EFOC is not suitable for long-range field or target use. Select "Dangerous game / EFOC build" in the calculator to see the relevant build score.
How should I set up my arrow for 3D archery?
For 3D archery, optimise for speed and trajectory flatness rather than penetration. Target 320–420 grains total weight, 8–12% FOC, and 5.5–7 GPP. Use a 75–100 grain field point, a standard aluminium insert (12–16 grains), and small low-profile vanes (1.75″–2″) with minimal helical. A faster, flatter arrow reduces the cost of distance estimation errors — the core skill challenge in 3D. Select 3D archery as the purpose in the calculator above to score your build against these targets. For 3D scoring, distances, divisions, and sight selection, see the 3D archery section of the Bow Sight Guide.