What Is a Micron? Definition and Examples

This carbon filament is 6 microns in diameter, while it rests on a human hair that is 50 microns thick.
This carbon filament is 6 μm or microns in diameter, while it rests on a human hair that is 50 microns thick. (photo: Anton, Creative Commons)

A micron is a unit of length that is one millionth of a meter or 10-6 m. One micron is 1/26,000 of a inch. The micron is also known as a micrometer (American), micrometre (International Bureau of Weights and Measures), or by its abbreviation μm. Usually, the plural form of a micron is “microns,” but before the year 1950 the word “micra” was used.

Examples of Objects Measured in Microns

The micron or micrometer is used to describe sizes of very small objects. An object that is a single micron across is only visible using magnification (a microscope), while objects that are 10 microns thick are barely visible without magnification. Generally, the human eye sees particles in the 50 to 60 micron range. Examples of objects measured in microns are:

  • 1-10 μm – Length of a bacterium
  • 10 μm – Size of hyphae of a fungus
  • 3-8 μm – Thickness of spider silk
  • 5 μm – Length of a human spermatozoa head
  • 10 μm – Droplet of fog or water droplet in a cloud
  • 10 μm – Diameter of human red blood cell
  • 10-12 μm – Thickness of plastic cling wrap
  • 10-55 μm – Thickness of sheep wool fiber
  • 17-181 μm – Diameter of human hair
  • 70-180 μm – Thickness of a sheet of paper

In some cases, the angstrom or nanometer are used as units instead of the micron or micrometer.


In 1879, the term micron and the symbol μ (Greek lowercase mu) were officially accepted as the distance equal to the micrometer. Using the term micron helped distinguish the unit from the measuring device called the micrometer. However, in 1967, the International System of Units (SI) revoked the official use in order to keep naming of units consistent.