How this instrument works
Front of Center, or FOC, describes how far forward of an arrow's true midpoint its balance point sits, expressed as a percentage of the arrow's total length. An arrow that balances exactly at its midpoint has 0% FOC; one balancing further toward the point has positive FOC, and the further forward that balance point sits, the higher the percentage.
FOC matters because where an arrow's mass sits changes how it flies. A more front-weighted arrow, with higher FOC, tends to recover from the paradox flex caused by leaving the bow more quickly, resist wind drift somewhat better, and retain more penetrating momentum on impact — which is why hunters in particular pay close attention to it. Very low or negative FOC can leave an arrow less stable in flight, while pushing FOC extremely high can make an arrow feel sluggish off the bow and drop more in trajectory over distance.
Measuring FOC starts with finding the physical balance point: balance a fully built arrow, with point, insert and fletching all attached, across a level edge or dedicated FOC tool, and mark where it settles. Measure the distance from that balance point back to the nock throat — the base of the nock groove — and that measurement, along with the arrow's total length, is everything the formula needs.
- Balance the fully assembled arrow (point, insert and fletching attached) across a level edge to find where it settles.
- Enter Balance point from nock end (in) — the distance from the nock throat to that balance point.
- Enter Total arrow length (in) — the full length of the arrow, from nock throat to the tip of the point.
- Read Front of Center (%) — the resulting FOC figure for that specific arrow build.
- Total length must be greater than zero, and the balance point can't be negative — the instrument will prompt you if either is invalid.
Worked example — a 28-inch arrow balanced at 15 inches
Enter 15 into Balance point from nock end (in) and 28 into Total arrow length (in) — a 28-inch arrow that balances 15 inches from the nock throat. Front of Center reads 3.571%.
The arrow's true midpoint sits at 28 ÷ 2 = 14 inches from the nock, so the balance point at 15 inches is 1 inch forward of that midpoint. Dividing that 1-inch offset by the 28-inch total length and multiplying by 100 gives (1 ÷ 28) × 100 = 3.571% — on the low end of typical FOC ranges, since archers commonly build target and hunting arrows to balance considerably further forward than this.
Questions
What FOC percentage should I be aiming for?
It depends on the discipline and personal tuning preference — Easton's published guidance puts indoor target arrows around 7-15% FOC, outdoor target arrows around 10-15%, and hunting setups in that same 10-15% band, favoured for the momentum and penetration bowhunters want. Treat any specific figure as a starting point to tune from rather than a fixed rule, since arrow spine, point weight and bow setup all interact with it, and pushing much past 20% tends to cost stability rather than add it.
How do I physically find my arrow's balance point?
Balance the fully built arrow — point, insert and fletching all attached, since each changes the balance — across a level edge, a coin, or a dedicated FOC balancing tool, and note where it settles without tipping either way. Measure from that spot back to the nock throat, the base of the nock groove, and that distance is the 'balance point' this calculator needs.
Is higher FOC always better?
No — pushing FOC very high, usually by adding a heavier point, can make an arrow feel sluggish leaving the bow and drop more over distance even though it may penetrate deeper on impact. Most tuning guidance treats FOC as one factor to balance against arrow spine, point weight and intended use, not a number to maximise on its own.
What causes low or negative FOC, and is it a problem?
Low or negative FOC usually comes from a light point paired with heavy fletching or a long, heavy nock end, shifting the balance point back toward or behind the true midpoint. It can leave an arrow less stable recovering from paradox flex off the bow, so most tuning guidance recommends at least some positive FOC rather than a balance point sitting at or behind the arrow's midpoint.
Does changing point weight affect FOC more than changing fletching does?
Generally yes — the point sits at the very front of the arrow, so a given change in point weight shifts the balance point by more than an equivalent weight change at the fletching end, which sits closer to the arrow's centre of mass already. Swapping to a heavier point is the most common way archers deliberately raise FOC on an existing arrow build.
Do target archery and hunting arrows aim for different FOC?
Yes, typically — target and indoor arrows are often built toward the lower end of common FOC guidance, prioritising flat trajectory and forgiveness at known distances, while hunting arrows are frequently built with more front weight to favour penetration and quicker paradox recovery on impact. Neither approach is universally 'correct'; both are tuning choices matched to how the arrow will actually be used.