Micrometers to Millimeters
Convert micrometers to millimeters instantly — one micrometer is 0.001 millimeters.
| Micrometers | Millimeters |
|---|---|
| 1 µm | 0.001 mm |
| 2 µm | 0.002 mm |
| 3 µm | 0.003 mm |
| 5 µm | 0.005 mm |
| 10 µm | 0.01 mm |
| 25 µm | 0.025 mm |
| 50 µm | 0.05 mm |
| 100 µm | 0.1 mm |
How to use
- Enter a value in the Micrometers field.
- The Millimeters figure appears immediately — no button to press.
- Typing in the Millimeters field converts back to Micrometers the same way.
- Use the reference table for the values that come up most often.
Micrometers to Millimeters formula
The factor from micrometers to millimeters is 0.001.
mm = µm × 0.001
Put another way, one micrometer is exactly 1/1,000 of a millimeter.
Why this factor: the micrometer and the millimeter are both defined against the meter, so dividing one definition by the other gives 0.001 directly. Both definitions are set out in full below.
To go the other way, divide by 0.001 — or use the Millimeters to Micrometers converter, which is the same calculation reversed.
Worked example
Take 5 µm and multiply by the factor 0.001: the result is 0.005 mm.
5 µm × 0.001 = 0.005 mm
The converter above does this for any value you type, in either direction.
What is a micrometer?
A micrometer, or micron, is one millionth of a meter — the scale of cells, fibers and semiconductor features.
Definition: Exactly 1×10⁻⁶ meter by SI prefix definition. Symbol µm.
Where it is used: Filtration ratings, particulate sizes (PM2.5 is 2.5 µm), fiber diameters, optical wavelengths.
Worth knowing: Often written 'micron' in industry. A human hair is roughly 70 µm across.
What is a millimeter?
A millimeter is one thousandth of a meter — the working precision unit of manufacturing and construction.
Definition: Exactly 0.001 meter by SI prefix definition.
Where it is used: Engineering drawings, machining tolerances, timber and steel dimensions, rainfall totals.
Micrometers vs Millimeters
The micrometer and the millimeter belong to the same family of units, so converting between them is usually a matter of shifting a decimal point or applying a small whole-number factor.
Frequently asked questions
How many millimeters are in a micrometer?
One micrometer equals 0.001 millimeters.
What is the formula to convert micrometers to millimeters?
Multiply the number of micrometers by 0.001. To reverse it, divide by 0.001 instead.
How do I convert millimeters back to micrometers?
Divide by 0.001, which is the same as multiplying by 1000.
How many millimeters are in 10 micrometers?
10 µm works out to 0.01 mm.
Is there anything to watch out for with micrometers?
Often written 'micron' in industry. A human hair is roughly 70 µm across.
How is the micrometer defined?
Exactly 1×10⁻⁶ meter by SI prefix definition. Symbol µm.