A grain of salt is a tiny crystal of sodium chloride, the compound that table salt is made of. Morton's iodized table salt is mostly cubes 0.2–0.6 millimeters across. The explorer shows a grain 0.5 millimeters, or 500 micrometers, wide. A micrometer is a millionth of a meter.

Size

Salt makers sort their grains with screens, sieves with holes of a set size. Morton's iodized table salt is taken from the middle size range of the salt Morton produces. No more than 5% of it is caught by a screen with holes 600 micrometers wide, and no more than 9% falls through holes 212 micrometers wide. So at least 86% of it is in grains between 0.2 and 0.6 millimeters across.

In a 2025 article for the University of California's Master Food Preserver program, Henry Shaw photographed several salts through a microscope. His canning salt was made of very even grains: rounded cubes about 0.5 millimeters across. Flake salts had larger, irregular pieces.

Size comparisons

• A grain 0.5 millimeters wide is about five times as wide as a human hair.
• About 130 grains lined up in a row would stretch across a tennis ball, which is about 6.7 centimeters (2.6 inches) wide.
• A 0.7-millimeter mechanical pencil lead is 1.4 times as wide as the grain.
• The grain would cover about 1.6 pixels of a 27-inch full-HD computer monitor.
• If a grain of salt were enlarged to the width of Earth, its neighboring ions would be about 7 meters (24 feet) apart.

What a grain is made of

Salt is made of ions, atoms that carry an electric charge. It holds equal numbers of positive sodium ions and negative chloride ions, packed in a regular pattern that repeats in every direction. Each ion is surrounded by six ions of the other kind, and the pattern is built from cubes.

A sodium ion has a radius of 102 picometers and a chloride ion 181 picometers. A picometer is a trillionth of a meter. The ions touch, so the centers of neighbors are 283 picometers apart.

About 1.8 million ions, alternately sodium and chloride, line each edge of a grain 0.5 millimeters wide. The whole grain holds about 5.5 × 10¹⁸ ions, or 5.5 billion billion.

How table salt is made

Table salt such as Morton's is vacuum pan salt. In 2019, nearly all vacuum pan salt made in the United States came from underground salt beds. Water pumped down dissolves the salt, and the salty water, called brine, is brought up and heated, sometimes under a vacuum, until the water evaporates.

The salt left behind crystallizes in the typical cube shape. Salt dried in open pans usually forms flakes instead.

Only a small share of salt ends up this way. In 2025, vacuum pan salt made up about 9% of the salt sold or used in the United States. The biggest users of salt were the chemical industry, with about 42% of sales, and highway deicing, with about 37%.

Sources

• Morton Iodized Table Salt, 26 oz. Food Service Rounds: Product Data Sheet 2516. Morton Salt, 2023.
• Salt, the Only Rock We Eat!. Henry Shaw, UC Master Food Preserver Program, University of California Agriculture and Natural Resources, 2025.
• Ionic Bonding. In Chemistry 2e. OpenStax, 2019.
• Lattice Structures in Crystalline Solids. In Chemistry 2e. OpenStax, 2019.
• Salt. In 2019 Minerals Yearbook. U.S. Geological Survey.
• Salt. In Mineral Commodity Summaries 2026. U.S. Geological Survey, 2026.
• Just How Small Is "Nano"?. National Nanotechnology Initiative.
• Rules of Tennis 2026. International Tennis Federation, 2026.
• Earth Fact Sheet. NASA, 2024.
• Dell 27 Monitor - E2724HS. Dell.