How to Convert Micrometres to Millimetres (µm to mm)
Length conversions come up when reading overseas furniture specs, cycling the Round Island Route in kilometres while a foreign app shows miles, or checking marine distances in the Singapore Strait in nautical miles. This guide shows how to convert micrometres into millimetres by hand, with examples and a quick-reference table.
The conversion
To convert micrometres to millimetres, multiply the value by 0.001. To go the other way, divide by the same number (or multiply by 1,000). For a quick estimate, multiply by about 0.001.
Millimetres = micrometres × 0.001
Worked examples
- 3 µm = 0.003 mm
- 12.5 µm = 0.0125 mm
- 75 µm = 0.075 mm
Micrometres to Millimetres table
| Micrometres | Millimetres |
|---|---|
| 1 µm | 0.001 mm |
| 2 µm | 0.002 mm |
| 5 µm | 0.005 mm |
| 10 µm | 0.01 mm |
| 20 µm | 0.02 mm |
| 25 µm | 0.025 mm |
| 50 µm | 0.05 mm |
| 100 µm | 0.1 mm |
| 250 µm | 0.25 mm |
| 500 µm | 0.5 mm |
| 1,000 µm | 1 mm |
Common questions
Is µm to mm exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Millimetres to Micrometres converter.
Mistakes to avoid
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Background
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
Many conversion factors are exact by definition. The inch has been defined as exactly 2.54 centimetres since 1959, and the pound as exactly 0.45359237 kilograms, so conversions involving them can be as precise as you need.
For any value, use the Micrometres to Millimetres Converter or browse all length converters.
Run your own numbers: Micrometres to Millimetres Converter