Shotgun Shot String & Pattern Calculator

A shotgun does not fire a single projectile but a cloud of pellets, and whether you break the clay or bag the bird depends on how many of those pellets land where you point. This calculator estimates total pellet count from your payload and shot size, then applies the choke and distance to predict density inside the standard 30-inch circle.

How it works

Two facts drive the calculation. First, pellet count comes from shot size and payload:

total_pellets = pellets_per_ounce(shot_size) * payload_ounces

Lead pellets-per-ounce are well-tabulated (e.g. #9 ≈ 585, #8 ≈ 410, #7.5 ≈ 350, #6 ≈ 225, #4 ≈ 135). Second, choke is defined by the percentage of pellets inside a 30-inch circle at 40 yards:

Adjusting for distance

The pattern opens roughly with the square of distance, so the fraction of pellets caught by a fixed circle scales as (40 / distance)², clamped to a sensible maximum near the muzzle. Pellets on target is then total_pellets * pattern_fraction.

Choosing shot size and payload for the target

Shot size is a trade-off between pellet count and individual pellet energy. Larger shot (lower number) carries more energy per pellet and retains velocity better at range, but the payload contains fewer pellets, thinning the pattern. Smaller shot (higher number) delivers more pellets per ounce but they slow faster and carry less punch at distance.

For upland birds and clay targets at typical ranges (15–35 yards), #7.5 or #8 is the most common choice. A standard 1-1/8 oz load of #8 contains around 460 pellets — enough to give dense coverage even with an open choke.

For waterfowl (and everywhere lead is prohibited), non-toxic shot such as steel or bismuth must be used. Steel shot is harder and denser per unit volume but lighter per pellet than lead, so you typically need one or two shot sizes larger in steel than you would use in lead to achieve comparable downrange energy.

For longer crossing shots on pheasant or dove (30–45 yards), #6 or #7.5 gives more pellet energy at range, though the total pellet count in the circle drops.

Reading the density result

The pellet count inside the 30-inch circle is a density number. Field guides and gunwriters have proposed various minimum thresholds over the years, and while there is no universal standard, a widely repeated guideline is:

• Upland game birds: at least 100–130 pellets in the 30-inch circle for reliable coverage at the intended range.
• Clay targets: pattern density matters less per pellet since you are breaking a small disc, not needing penetration depth. A hit anywhere on the target counts, so pattern evenness matters more than raw count.

If the tool shows your pattern dropping significantly below these illustrative levels at your target range, your options are: tighten the choke, increase payload weight, move up in shot size, or accept a shorter effective range.

Choke and clay discipline matching

Choosing choke by discipline is as important as choosing by range:

• Skeet: Station 1 and 7 shots are very close; cylinder or skeet choke is standard. Tight chokes leave too small a hit window on targets crossing inside 20 yards.
• Trap: Singles leave the house going away and are typically 35–45 yards by the time you fire; modified to full is conventional.
• Sporting clays: Varies by station. Incoming close targets suit open chokes; long crossing targets suit tighter ones. Many sporting shooters carry two guns or a gun with interchangeable chokes.

Tips

If your bird load drops below about 100 pellets in the circle, you are at the edge of your effective range — step up payload weight before tightening the choke, since tightening choke helps more at marginal ranges than at the centre of the pattern. For clays, denser is not always better: an over-tight pattern is hard to center on a fast-crossing target, which is why skeet shooters favour open chokes at close stations.