Wind Drift Calculator

Horizontal drift — wind from your right pushes the arrow left. Wind from your left pushes it right. Quartering winds split into left/right and head/tail components, and both are applied.

Vertical (wind) — a headwind raises airspeed, which raises drag, so the arrow arrives later and drops more (↓). A tailwind does the reverse (↑). Each figure compares the windy shot with the same shot in still air at that same distance. Your sight was zeroed on a calm day, so the line of sight is fixed by the calm trajectory and cancels out of the comparison — which is why there is no sight-in distance to enter: it would cancel out of the arithmetic anyway.

Why drift happens at all — an arrow weathervanes into the apparent wind, so its drag vector tilts downwind and pushes it sideways. That is the same physics as the standard lag-time result used in rifle ballistics: drift equals crosswind speed times the difference between the real time of flight and the time a drag-free arrow would take. It also means more drag equals more drift — bigger vanes and slower arrows both cost you.

Model — full three-axis numerical integration of quadratic drag against the relative air vector, plus a yaw degree of freedom: the shaft is free to swing about its balance point under the aerodynamic restoring moment, rather than being assumed already aligned with the apparent wind. Centre of pressure comes from a Barrowman component build-up (point, shaft cross-flow, fletching, and broadhead blades where fitted); the balance point comes from your FOC; the rotational inertia comes from the mass split those two imply. Head, tail and quartering winds change time of flight, drop and drift together rather than being patched in afterwards. Effective Cd = 2.5 on frontal area, which rolls shaft skin friction and vane drag into one calibrated figure; it reproduces roughly 25–27 fps of loss over 60 yards for a 450 gr / 0.245″ arrow launched at 280 fps. Expect about ±15% on a well-described setup. Real wind is gusty and rarely full value across the whole flight path, which is a larger error than the model's.

Broadheads — a fixed-blade head costs you twice, and the second cost is the bigger one. First, drag: blades ride edge-on to the airflow, so their drag comes from blade count × stock thickness × exposed blade height against the shaft's own frontal area. A three-blade 1⅛″ head on a 0.245″ shaft works out near +40%. Second, and worse: those blades sit ahead of the balance point, where they act as forward lifting surfaces. They drag the centre of pressure forward, eat most of your stability margin, and leave the shaft sitting at a larger yaw angle for longer in a crosswind — which is what actually pushes the arrow off line. On a 28″ arrow at 15% FOC that same head cuts the stability margin from about 41% of length to about 15%, and roughly doubles total drift at 40 yards. Drag alone would have predicted a third of that. Mechanicals fly with the blades closed and are treated as a field point plus a nominal 3% for the ferrule. Blade stock is assumed at 0.030″ and blade length at 0.9 × cut diameter; a long single-bevel will read low here.

What FOC does — and what it cannot do — FOC is an input again, and it does something real, but not the thing it is usually credited with. A stable arrow yaws until it lines up with the apparent wind; that is what stability is for. Once it is lined up, angle of attack is zero, and the only force left is drag acting along the apparent wind — which still has a downwind component. So a perfectly stable arrow still drifts, by exactly the lag-time amount, and no amount of FOC can do better than that. The popular claim that a high-FOC arrow “turns into the wind” and therefore steers upwind imports a result from model rocketry, where weathercocking genuinely does push a rocket upwind — because a rocket has thrust along its axis. Point a thrusting rocket upwind and it flies upwind. An arrow is coasting: the axial force is drag, pointing backwards, so tilting the nose upwind tilts the drag vector downwind. Same geometry, opposite sign. Across 36 modelled configurations — field points and broadheads, 5 to 24% FOC, 5 to 20 mph — not one landed upwind of the lag-time floor.

So what is FOC worth? With a field point, almost nothing in wind: hold total arrow weight constant and sweep FOC from 5% to 24% and drift at 40 yards moves about 0.14″, with a shallow best point near 19%. The large drift reduction archers do see from heavy points is mostly the weight, not the balance — and weight is already an input above. Where FOC earns its keep is with broadheads: the planing penalty falls from roughly +4″ at 10% FOC to about +1.4″ at 24%. High FOC is a broadhead fix, not a crosswind fix. One caveat in the other direction: this model treats the arrow as rigid and launched cleanly, so it does not price shaft flex or a bad release, both of which high FOC also helps with.