Micrometer Converter (µm)
Enter a length in any unit below and this converter instantly shows the equivalent value in all other units. Micrometers (µm, also called microns) are the standard unit for measuring cells, wavelengths, surface roughness and precision machining tolerances. Switch the input unit to convert from nanometers, millimeters, inches or any other length into micrometers and every other unit at once.
What is a micrometer (µm)?
A micrometer, symbol µm, is a unit of length in the International System of Units (SI) equal to one millionth of a meter (10-6 m) or one thousandth of a millimeter. The informal name "micron" is widely used in science and industry. The word comes from the Greek "mikros" (small) and was formally adopted by the SI in 1967. Because a micrometer sits between the nanometer (10-9 m) and the millimeter (10-3 m) on the scale of measurement, it is the natural unit for biological cells, optical wavelengths, airborne particles, precision machining tolerances, and thin-film coatings.
How to use this converter
Select the unit you are starting from in the "Input unit" drop-down, type your value, and all equivalent lengths update instantly. The converter handles 13 units across metric and imperial systems: picometers, nanometers, micrometers, millimeters, centimeters, meters, kilometers, inches, feet, yards, miles, nautical miles, and microinches. To reverse a conversion, simply change the input unit to the one you want to start from. For example, to convert 1 inch to micrometers, select "Inch (in)" and enter 1, the micrometer output will read 25,400 µm.
Key conversion formulas
The anchor relationships are: 1 µm = 0.001 mm = 1,000 nm = 1,000,000 pm = 0.000001 m. For imperial conversions, the exact legal definition gives 1 inch = 25,400 µm, so 1 µm = 1/25,400 inch = 3.937 × 10-5 in. One foot = 304,800 µm. To convert millimeters to micrometers multiply by 1,000. To convert nanometers to micrometers divide by 1,000. To convert micrometers to inches divide by 25,400.
Practical uses of the micrometer scale
Biology and medicine use micrometers for cell diameters (red blood cells 6-8 µm, E. coli bacteria 1-5 µm, human hair 17-180 µm). Air quality regulations define PM2.5 (particles smaller than 2.5 µm) and PM10 (smaller than 10 µm). Semiconductor manufacturing describes transistor gate lengths in nanometers (fractions of a µm). Surface metrology uses Ra (average roughness) values from 0.025 µm for mirror-polished surfaces to 50 µm for rough castings. Optical fiber cores are 8-62.5 µm in diameter, and the wavelength of visible light ranges from 0.38 µm (violet) to 0.70 µm (red).
Common measurements in micrometers
| Object / Material | Size (µm) | Notes |
|---|---|---|
| Atom diameter | 0.0001-0.0005 | Carbon atom ~0.00015 µm |
| DNA double helix width | 0.002 | 2 nm |
| HIV virus | 0.1 | 100 nm |
| Bacterium (E. coli) | 1-5 | Typical rod-shaped bacterium |
| Red blood cell | 6-8 | Human erythrocyte |
| Human platelet | 2-3 | Blood clotting cell |
| Fine beach sand | 63-250 | USGS sand classification |
| Human hair (diameter) | 17-181 | Fine to coarse hair |
| Fine dust (PM2.5) | below 2.5 | Lung-penetrating particles |
| Coarse dust (PM10) | below 10 | Inhalable particles |
| Sheet of paper | 70-180 | Standard printing paper |
| Human eye resolution | 100-200 | Smallest detail eye can resolve |
| Inch | 25,400 | 1 in = exactly 25,400 µm |
| Millimeter | 1,000 | 1 mm = 1,000 µm exactly |
| Visible light (red) | 0.7 | 700 nm wavelength |
| Visible light (violet) | 0.38 | 380 nm wavelength |
| Surface roughness Ra | 0.025-50 | Precision machining range |
Real-world sizes in µm (microns) for quick reference.
Frequently asked questions
How many micrometers are in a millimeter?
There are exactly 1,000 micrometers in one millimeter. To convert millimeters to micrometers multiply by 1,000; to convert micrometers to millimeters divide by 1,000. This is because 1 mm = 10-3 m and 1 µm = 10-6 m, so the ratio is 1,000.
How many micrometers are in an inch?
By the international definition adopted in 1959, there are exactly 25,400 micrometers in one inch (because 1 inch = 2.54 cm = 25.4 mm = 25,400 µm). To convert micrometers to inches divide by 25,400. To convert inches to micrometers multiply by 25,400.
What is the difference between a micrometer and a micron?
They are the same thing. "Micron" is an older informal name for the micrometer (µm). The SI officially recommends "micrometer," but "micron" is still widely used in biology, materials science, and industry. Both refer to a length of one millionth of a meter.
How do I convert micrometers to nanometers?
Multiply the micrometer value by 1,000. One micrometer equals 1,000 nanometers because 1 µm = 10-6 m and 1 nm = 10-9 m, giving a factor of 1,000. For example, 0.7 µm (red light wavelength) = 700 nm.
What objects are measured in micrometers?
Common objects measured in micrometers include: biological cells (red blood cells at 6-8 µm, bacteria at 1-5 µm), human hair diameter (17-180 µm), airborne particles (PM2.5 and PM10), machining surface roughness (Ra values 0.025-50 µm), optical fiber cores (8-62.5 µm), wavelengths of visible and infrared light (0.38-1,000 µm), and thin-film coatings in semiconductors.
How many micrometers are in a meter?
There are exactly 1,000,000 micrometers in one meter. The prefix "micro" means 10-6 (one millionth), so 1 m = 1,000,000 µm. To convert meters to micrometers multiply by 1,000,000 (or by 1e6). To convert micrometers to meters divide by 1,000,000.