How to measure a group correctly
Group size is the center-to-center distance between the two outermost arrows in a group. Not edge-to-edge. Not a visual estimate from five feet back. Center-to-center, with a ruler or calipers.
For a round shaft in a round hole, the conversion is simple: measure edge-to-edge of the two outermost holes, then subtract one shaft diameter. A 5mm shaft is 0.197". A 4mm shaft is 0.157". A 9/32" indoor shaft is 0.281". That subtraction is not optional — ignoring it consistently overstates your group by the diameter of the shaft, and it makes comparisons between setups meaningless unless both are shooting the same diameter.
Every arrow in the group counts. The instinct to pull the one bad arrow and measure the remaining cluster is understandable — but that arrow is data. If you exclude it, you are measuring your average shots rather than your system. The system includes the outlier.
You can use it diagnostically — pull the flier, note its direction, and investigate whether it has a consistent pattern — but for group measurement purposes it stays in.
Sample size: why three arrows tells you almost nothing
Three-arrow groups are common on social media and nearly useless as a measurement tool. Three random samples drawn from any normal distribution can cluster tightly or spread widely by chance. When extreme spread is your metric, the variance of the measurement itself is enormous at n=3. You are mostly measuring luck.
Ten arrows is the minimum for a group size number that carries any real information. At ten shots the measurement becomes stable enough that repeating it gives similar results — the underlying σ of the system starts to reveal itself rather than the random walk of three draws. Twenty arrows is better still when you are trying to identify whether a specific arrow in a batch is an outlier.
The practical implication: when you change one variable — tuning, arrow, nock, rest position — and then shoot a 3-arrow group to evaluate it, you are not evaluating the change. You are mostly rolling dice. Shoot ten. The session takes ten minutes longer and the information is worth having.
The 1-inch-per-10-yards rule
The rule is: you should expect your group to grow by roughly one inch for every ten yards of distance. A 1" group at 10 yards, 2" at 20, 4" at 40, 6" at 60.
It is a useful field heuristic that is approximately right in a specific middle range, and wrong everywhere else.
Where it holds
For a hunting-class compound bow with a practiced archer, decent arrows, and at least basic tuning, the 1"/10yd rule is a reasonable ballpark from about 20 to 50 yards. In that window, the dominant error sources — form variation and minor tune residue — scale roughly linearly with distance, because the arrow's time of flight increases linearly and the lateral displacement from a given angular error scales with time of flight.
Where it breaks short
At very close distances — under 15 yards — the rule tends to be pessimistic, because the arrow barely has time in the air to express form error before it arrives. But at 20 yards, a 2" group is realistic for a solid recreational archer with a well-tuned bow. The rule is not obviously wrong in the 20–50 yard window for the typical archer. The mistake is assuming it holds as a constant — it describes a linear model, and the real world is not linear.
Where it breaks long
Beyond 60 yards the rule gets optimistic for two reasons. First, wind. Even a light steady breeze opens groups significantly at 80 and 100 yards because the arrow is in the air for longer and wind variation — gusts, lulls, timing differences between shots — becomes the dominant error source. Wind contribution to group size does not scale linearly; it grows faster than distance. Second, aiming precision. The sight picture at 80 yards puts a smaller target behind a larger pin relative to 40 yards. The aperture size that looked fine at 40 yards starts to cost you at distance.
A hunting archer shooting a 4" group at 40 yards will not shoot an 8" group at 80 yards — they will shoot 12–16" or worse once wind is a factor. The rule implies linear scaling; the physics is not linear.
What actually scales linearly
A mechanical device — a hooter shooter, a shooting machine — produces groups that do scale roughly linearly with distance in calm conditions, because it eliminates the human error term. What remains is arrow-to-arrow consistency, tuning residue, and minor aerodynamic variation. Those sources are proportional to flight time and therefore to distance. The 1"/10yd rule is a reasonable model for machine performance. It was never a particularly good model for human archers, especially at distance in wind.
What is actually good — benchmarks by setup and distance
These are ten-arrow center-to-center groups in calm to light conditions. The tiers below are honest about the skill level required — not just the equipment. A person who practices twice a week and shoots tournaments is not the same archer as someone on a national team, even if they own the same bow.
20 yards / indoor
Hooter shooter or shooting machine: 0.3–0.5". Wider than 0.75" points to a tune or arrow consistency problem.
Elite competitive archer (national/world team level, full-time training, top 3D professionals): 0.75–1.25". This is exceptional. A handful of people per state are consistently in this range.
Strong club or regional competitive archer (regular tournament schedule, consistent practice, good equipment and full tuning): 1.5–2.5". This is a realistic ceiling for an archer who takes the sport seriously and puts in real practice time.
Recreational compound archer (shoots regularly, decent equipment, basic tuning): 2.5–4". This is where most people with good setups actually land.
Hunting setup, practiced archer: 3.5–5".
Basic hunting bow or partial tuning: 5–8".
40 yards
Elite competitive archer: 2.5–4". Again — this requires full-time or near-full-time dedication. Not a "serious hobbyist."
Strong club or regional competitive archer: 4–6". A solid, experienced archer who shoots outdoors regularly and has done the tuning work.
Recreational compound archer, good setup and tuning: 6–9". Honest mid-range for someone who practices and has put real effort into their equipment.
Hunting setup, fully tuned, practiced archer: 7–10".
Basic hunting bow, standard tuning: 10–14".
Store-bought arrows, minimal tuning: 14" or wider. This is not a criticism — it is an honest accounting of what those variables contribute.
60 yards
Elite competitive archer: 4–7" in light wind. At 60 yards outdoor conditions start to matter even on calm days.
Strong club / regional archer: 7–11".
Hunting setup, fully tuned, practiced: 10–15". This is inside the ethical hunting range for a practiced archer with a kill-zone margin — but only just, and only in calm conditions.
Basic hunting / partial tuning: 15"+ in any real-world conditions. Most experienced hunters recognize this distance as past their personal ethical limit.
80 yards and beyond
Group size at 80+ yards is highly environment-dependent. Outdoors with any consistent wind, groups from any equipment will be 50–100% wider than 60-yard performance, because wind timing variation between shots becomes the dominant error term.
Hunting at this distance is a domain for a very small number of archers — extraordinary practice volume, premium equipment, and ideal conditions are all required simultaneously. Group size at 80 yards in practice still does not fully predict performance under field conditions and adrenaline.
The mechanical ceiling — and why most archers never reach it
There is a useful distinction between what the equipment can do on a shooting machine and what a human archer actually produces. The machine number is the mechanical ceiling — it removes all human error and shows what remains: arrow-to-arrow consistency, tuning residue, aerodynamic variation.
Most archers are nowhere near that ceiling. The ceiling is a lower bound on group size, not an expectation. The gap between the ceiling and actual performance is almost entirely the archer — form variation, timing inconsistency, aiming error, and shot-to-shot execution.
Budget bow, store arrows, no dedicated tuning: Mechanical ceiling around 5–6" at 40 yards. The arrow variation is baked in. The realistic goal is to be consistent enough that the equipment, not the archer, is the limit.
Hunting bow, basic tune, quality arrows: Ceiling around 3–4" at 40 yards. Most practiced hunters will land between this ceiling and twice it depending on practice volume and conditions.
Hunting bow, fully tuned, DIAG or bareshaft verified: Ceiling around 2–2.5" at 40 yards. Getting to the ceiling requires genuinely consistent execution — this is where shot process becomes the bottleneck, not equipment.
Target-class setup, long ATA, premium arrows: Ceiling around 1–1.5" at 40 yards. Reaching the ceiling at this level requires elite-tier execution. The equipment is no longer the limiting variable by a wide margin.
What group size cannot tell you
Group size measures total system spread. It does not tell you what caused it. Two setups can produce identical 4" groups at 40 yards for completely different reasons — one might have excellent arrow consistency and poor tuning; the other perfect tuning and inconsistent arrows; a third both reasonably good but with a form flaw that produces a consistent pattern. The group diameter is the same. The diagnosis is different.
This is why group center matters alongside group size. A tight group that is consistently two inches left of point of aim is useful information — it points to a specific cause. A group of the same size that is randomly scattered around point of aim points to a different one. Group size alone loses that signal.
The group size projection calculator lets you model what your specific combination of equipment and tuning depth should produce, and shows which factor is contributing the most spread. It won't diagnose a specific cause — but it can show whether your actual groups are tracking close to the mechanical ceiling or falling well short of it, which tells you whether to look at the setup or the execution.