A glass marble is a small, hard glass ball used as a playing piece in children's games. A standard marble is about 1.6 centimeters (5/8 inch) across. The explorer's picture shows a clear glass marble with a twist of colored glass inside.

Size

Marbles are made in several sizes, so the clearest standard comes from the rules of the game. The National Marbles Tournament, first held in 1922, is played each summer in Wildwood, New Jersey. Its rules call for 13 identical target marbles made of glass, each a standard 5/8 inch across. That is 15.9 millimeters, or about 1.6 centimeters.

Each player also has a shooter, the marble flicked at the targets. A shooter can be glass or stone but not metal. It must be between 1/2 and 3/4 inch (1.3–1.9 centimeters) across, and shooters are checked for size before the tournament begins.

Size comparisons

The largest shooter allowed, 3/4 inch across, is exactly as wide as a U.S. penny. A standard marble is five-sixths as wide as a penny.
A standard marble is about 1.6 times as wide as a 1-centimeter microwave is long.
About 15 standard marbles side by side would stretch across a basketball.
The circle in a tournament game is 10 feet (3.05 meters) across, the width of 192 standard marbles in a row.
If Earth were shrunk to the size of a standard marble, the Moon would be a bead about 4 millimeters across, 48 centimeters (19 inches) away.

How the tournament game is played

The tournament game is played on a concrete square 12 feet (3.7 meters) on a side, with the circle painted in the middle. The 13 target marbles are set in an X at the center, 3 inches (7.6 centimeters) apart. Players shoot in turn from outside the circle, with at least one knuckle of the shooting hand touching the playing surface.

A player scores one point for each target marble knocked out of the circle. A player who knocks one out, and whose shooter stays inside the circle, shoots again. A game lasts six innings, and a player who knocks out seven or more marbles in the first inning wins at once.

How glass marbles came to be

The earliest marbles were made of stone or clay. In the middle of the 19th century, a German glassblower invented special scissors for cutting hot glass, which made glass marbles affordable for the first time. Machines later made them faster and more cheaply still. In the United States, the M.F. Christensen and Son Company received a patent for a glass-marble-making machine in 1905.

By the 1920s, the Akro Agate Company of Clarksburg, West Virginia, was the largest marble maker in the world. Marbles joined the National Toy Hall of Fame in 1998. US federal rules require a choking-hazard warning on marbles made for children aged three and older.

Sources

Tournament Rules. National Marbles Tournament.
The National Marbles Tournament. National Marbles Tournament.
16 CFR 1500.19: Misbranded toys and other children's articles. US Consumer Product Safety Commission, Electronic Code of Federal Regulations.
Marbles. The Strong National Museum of Play, 2021.
The History of the Machine-Made Glass Marble. Museum of American Glass in West Virginia.
Coin Specifications. United States Mint, 2026.
Official Basketball Rules 2026: Basketball Equipment. FIBA, 2026.
Earth Fact Sheet. NASA, 2024.
Moon Fact Sheet. NASA, 2024.

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