How to Convert Millimetres to Micrometres (mm to µm)
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 millimetres into micrometres by hand, with examples and a quick-reference table.
The conversion
To convert millimetres to micrometres, multiply the value by 1,000. To go the other way, divide by the same number (or multiply by 0.001). For a quick estimate, multiply by about 1,000.
Micrometres = millimetres × 1,000
Worked examples
- 3 mm = 3,000 µm
- 12.5 mm = 12,500 µm
- 75 mm = 75,000 µm
Millimetres to Micrometres table
| Millimetres | Micrometres |
|---|---|
| 1 mm | 1,000 µm |
| 2 mm | 2,000 µm |
| 5 mm | 5,000 µm |
| 10 mm | 10,000 µm |
| 20 mm | 20,000 µm |
| 25 mm | 25,000 µm |
| 50 mm | 50,000 µm |
| 100 mm | 100,000 µm |
| 250 mm | 250,000 µm |
| 500 mm | 500,000 µm |
| 1,000 mm | 1,000,000 µm |
Common questions
Is mm to µm 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 Micrometres to Millimetres converter.
Mistakes to avoid
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.
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Background
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
For everyday use, three or four significant figures are usually enough. Engineering, science and trade documents may need more, and rounding should happen only at the end of a calculation.
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 Millimetres to Micrometres Converter or browse all length converters.
Run your own numbers: Millimetres to Micrometres Converter