Return to Scale View
About

How big is a Grain of Salt?

500 micrometers!

View History Report
Grain of Salt

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

Scale of the Universe > Grain of Salt
LCD Pixel
Although the size of pixels differs greatly, 300 micrometers is about the average. Pixels contain three subpixels that are red, green, and blue. Pixels are pretty cool, but voxels are even better. They are three-dimensional pixels.
Dust Mite
Dust mites like to eat dust, which you probably know is just dead skin cells. Many people are allergic to dust mites. Some people are allergic to their poop. Either way, almost all people want to get rid of this pesky pest.
Paramecium
Paramecia vary quite a lot in size, between 50 and 330 micrometers. These little guys are protists and like to swim in water. They can move two millimeters per second!
Pencil Lead
People use pencil lead a lot. Oh, by the way, this is mechanical pencil lead. On another note, the largest pencil contained 2,000 kilograms of graphite. That's about three times heavier than a human! And by human I mean the heaviest human ever.
Duckweed
These are water lentils that float in ponds and other bodies of water. They don't have stems or roots. On the other hand, they do create flowers, which are the smallest of any plant on Earth.
Ant
You probably don't like ants. That's too bad. 15-25% of all land animals are ants! Whoa! That's a lot of ants! For every person on Earth, there are over one million ants!

Discussion