What Is 20 gauge

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Last updated: April 15, 2026

Quick Answer: 20 gauge is a measure of shotgun barrel diameter where the bore size is determined by the number of lead balls of that size needed to weigh one pound—specifically, 20 lead balls equal one pound. It is smaller than 12 gauge but larger than 28 gauge, commonly used for hunting birds and home defense.

Key Facts

20 gauge refers to a shotgun bore diameter of approximately 0.615 inches
The gauge system is based on how many lead balls of that diameter equal one pound
20 gauge shotguns are 30–40% lighter than 12 gauge models, making them ideal for smaller shooters
Used in 85% of youth and beginner shotgun training programs in the U.S.
Effective range for bird hunting with 20 gauge is typically 30–40 yards

Overview

20 gauge is a standard measurement for shotgun barrels, widely used in hunting, sport shooting, and home defense. It describes the bore diameter based on the weight of a solid lead sphere that fits inside the barrel.

The term 'gauge' originates from 19th-century British firearms manufacturing, where the number represented how many lead balls of that size it took to make one pound. For 20 gauge, it takes 20 lead balls to equal one pound, defining the internal diameter.

Bore diameter of a 20 gauge is approximately 0.615 inches, making it smaller than 12 gauge (0.729 inches) but larger than 28 gauge (0.550 inches).
Because of its reduced recoil, the 20 gauge is a preferred choice for young shooters and small-framed adults, improving accuracy and comfort.
It is commonly used in upland bird hunting, such as pheasant and quail, where lighter loads and faster handling are advantageous in dense cover.
Modern 20 gauge shotguns can fire 2.75-inch, 3-inch, or even 3.5-inch shells, offering flexibility in power and payload depending on the model.
Despite its smaller size, advancements in ammunition technology allow 20 gauge loads to be effective for home defense, especially with buckshot or slugs.

How It Works

The gauge system measures bore size indirectly by weight rather than direct diameter, a method dating back to early firearms development in Europe. This unique system remains standard in shotguns today, especially in the United States and UK.

Gauge Definition: The gauge number indicates how many lead balls of that bore diameter it takes to weigh one pound; lower numbers mean larger bores.
20 vs. 12 Gauge: A 12 gauge requires only 12 lead balls to make a pound, making it significantly larger and more powerful than 20 gauge.
Recoil Reduction: The 20 gauge produces about 30% less recoil than a 12 gauge, improving shot control and reducing shooter fatigue.
Shot Spread: With proper chokes, 20 gauge shotguns can achieve consistent patterns up to 40 yards, ideal for fast-moving game birds.
Ammunition Availability: Over 120 million 20 gauge shells are produced annually in the U.S., ensuring wide retail and online availability.
Barrel Length Options: Common barrel lengths include 26, 28, and 30 inches, with shorter barrels preferred for home defense and longer ones for field use.

Comparison at a Glance

Below is a comparison of common shotgun gauges highlighting key differences in performance, size, and use cases:

Gauge	Bore Diameter (inches)	Lead Balls per Pound	Typical Use	Recoil Level
10	0.775	10	Turkey hunting, waterfowl	Very High
12	0.729	12	Police, hunting, sport	High
16	0.662	16	Upland hunting (rare)	Moderate-High
20	0.615	20	Youth, birds, home defense	Moderate
28	0.550	28	Clay target shooting	Low

This table illustrates that 20 gauge strikes a balance between power and manageability. It is more versatile than smaller gauges and more accessible than larger ones, making it a top choice for entry-level and experienced shooters alike. Its popularity has grown steadily since the 1990s, especially in law enforcement training programs.

Why It Matters

Understanding 20 gauge specifications helps shooters select the right firearm for their needs, whether for sport, defense, or hunting. Its design balances effectiveness with usability, making it a cornerstone of modern shotgun culture.

Beginner Accessibility: The reduced weight and recoil make 20 gauge shotguns ideal for introducing new shooters to firearms safety and marksmanship.
Home Defense Suitability: Many compact 20 gauge models, like the Remington 870 Express, are favored for household protection due to manageable size and stopping power.
Environmental Adaptability: In dense brush or woodland, the 20 gauge’s quicker handling and reduced noise offer tactical advantages over larger models.
Cost Efficiency: 20 gauge ammunition typically costs 10–15% less per round than 12 gauge, reducing long-term training expenses.
Wildlife Conservation: Used in regulated bird hunting, 20 gauge helps enforce sustainable harvest practices by limiting range and spread.
Manufacturing Trends: Major brands like Mossberg and Winchester have increased 20 gauge production by 22% since 2015 due to rising consumer demand.

As firearm technology advances, the 20 gauge continues to evolve with improved shells, lighter materials, and ergonomic designs. Its enduring relevance underscores its role as a versatile and practical choice in the shotgun world.