Micrometers to Millimeters Converter
Enter a length in micrometers and the converter returns it in millimeters, rounded to four decimals. A millimeter is made of 1,000 micrometers.
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Created by the Reeliy Editorial Team. Last updated: Oct 19, 2026
How many micrometers are in a millimeter?
A millimeter is 1,000 micrometers. Both names carry SI prefixes: milli- means 10-3 and micro- means 10-6, so the ratio between them is 103. A micrometer (symbol μm, also called a micron) is therefore one millionth of a meter, or 0.001 mm.
millimeters = micrometers ÷ 1000To reverse it, multiply millimeters by 1000.
Dividing by 1,000 simply moves the decimal point three places to the left. 250 μm becomes 0.25 mm and 12 μm becomes 0.012 mm.
Getting a feel for the scale
Micrometers are the working unit for things too fine for a ruler but too coarse for atomic scales. A human hair is somewhere around 70 μm across, which is 0.07 mm. Typical office paper is roughly 100 μm (0.1 mm) thick. Red blood cells measure about 7 to 8 μm, and many bacteria are between 1 and 10 μm long.
In manufacturing, coatings, surface finishes, filter pore sizes and machining tolerances are given in micrometers, while the part itself is drawn in millimeters. Converting between the two lets you compare a 25 μm film with a 0.5 mm sheet on one scale.
How to convert micrometers to millimeters
- Enter the value in micrometers (μm) in the first box.
- The second box shows the equivalent length in millimeters.
- Remember that the answer is always a thousand times smaller than the input.
Example 1. A 25 μm coating: 25 ÷ 1000 = 0.025 mm.
Example 2. A 1,500 μm wire diameter: 1500 ÷ 1000 = 1.5 mm.
Example 3. A 120 μm filter mesh opening: 120 ÷ 1000 = 0.12 mm.
The converter prints four decimals, so its resolution is 0.0001 mm (0.1 μm). A value below 0.05 μm, such as 0.04 μm = 0.00004 mm, is displayed as 0. For finer values, use the micrometers to nanometers converter.
Micrometers to millimeters conversion table
| Micrometers (μm) | Millimeters (mm) |
|---|---|
| 0.5 | 0.0005 |
| 1 | 0.001 |
| 5 | 0.005 |
| 10 | 0.01 |
| 25 | 0.025 |
| 50 | 0.05 |
| 75 | 0.075 |
| 100 | 0.1 |
| 250 | 0.25 |
| 500 | 0.5 |
| 1,000 | 1 |
| 2,500 | 2.5 |
| 5,000 | 5 |
| 10,000 | 10 |
Related units and common mix-ups
- Micron. The older name for the micrometer. They are the same length.
- Mil. A mil is a thousandth of an inch (25.4 μm). It is not a millimeter and not a micrometer.
- mm versus μm. A slip of one prefix changes the size by a factor of 1,000. Check the symbol: the μ is a Greek mu.
Going the other way, the millimeters to micrometers converter multiplies by 1,000 for you.
Frequently asked questions
How many millimeters is one micrometer?
One micrometer is 0.001 millimeters, a thousandth of a millimeter.
Is a micron the same as a micrometer?
Yes. Micron is the older name for the micrometer, and both mean one millionth of a meter.
How do I convert μm to mm in my head?
Move the decimal point three places to the left. 4,500 μm becomes 4.5 mm.
How many micrometers are in 0.5 mm?
0.5 mm is 500 μm, found by multiplying the millimeters by 1,000.
References
Cite this converter and page
If you use this page in your work, you can cite it as:
Reeliy Editorial Team. (2026). Micrometers to Millimeters Converter. Reeliy. https://reeliy.com/converters/convert-micrometer-to-mm“Micrometers to Millimeters Converter.” Reeliy, 2026, https://reeliy.com/converters/convert-micrometer-to-mm.