How is the total pellet count calculated?

Each lead shot size has a known number of pellets per ounce — for example, US #8 is about 410 pellets per ounce and #6 about 225. The tool multiplies pellets per ounce by your payload weight in ounces to get the total in the shell.

What does the choke percentage mean?

Choke is rated by the percentage of the total pellets that land inside a 30-inch circle at 40 yards. Full choke is about 70 percent, modified 60 percent, improved cylinder 50 percent, and cylinder 40 percent. Tighter chokes concentrate more pellets but shrink the effective spread.

Why does pattern percentage fall off with distance?

The shot column spreads as it travels, so a fixed 30-inch circle captures a shrinking fraction of pellets the farther out you measure. The tool scales the choke's 40-yard rating up or down with distance to estimate the percentage at your range.

How many pellets do I need for a clean kill?

A common guideline is at least 3 to 5 pellet strikes on a game bird's vital area, which usually means keeping pattern density above roughly 100 to 130 pellets in the 30-inch circle for the target species. Use the count to judge your maximum effective range.

Does this account for shot string length?

The pellet count and pattern percentage are based on the standard 30-inch frontal pattern. True shot string is the lengthwise spread that affects crossing targets; this tool focuses on density, which is the dominant factor for choosing a load and choke.

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:

Choke	% at 40 yd
Cylinder	40%
Improved Cylinder	50%
Modified	60%
Improved Modified	65%
Full	70%

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.

Tips

If your bird load drops below about 100 pellets in the circle, you are at the edge of your effective range — step up shot size only if you keep enough pellet count, or tighten the choke. For clays, denser is not always better: an over-tight pattern is hard to center, which is why skeet shooters favor open chokes at close stations.