A micrometre, often called a micron, is a millionth of a metre. It is used for filter ratings, coating thickness, fibre diameters and particle sizes; a human hair is roughly 50–100 µm thick.
How to use the Micrometer
- Pick the unit you are starting from in the From menu and type your value.
- Pick the unit you want in the To menu. The heading changes to match – for example “Micrometers to Millimeters Converter”.
- The most common length units are shown below at the same time, so you can compare them at a glance.
- Type into any result to convert backwards, then use Copy results – the copied text starts with the heading for your chosen units.
Results update as you type. Everything is calculated in your browser.
How it works
Every length unit is defined by an exact factor relative to the metre (the base unit). The calculator first turns the value you type into metres, then turns that into the unit you picked in the “To” menu and into each of the common units below it. This two-step method means any unit can be converted to any other – 27 units are available in each menu – and you can type into any field, including a result, to work in the other direction. Changing a unit menu keeps the quantity the same and just re-expresses it, and the page heading and copied results follow your choice.
How to convert length units
- Choose the unit you have in the From menu and type the value, for example 25 µm.
- Choose the unit you want in the To menu, for example millimetres. The page heading changes to “Micrometers to Millimeters Converter”.
- The calculator multiplies by the metre factor of the “from” unit and divides by the factor of the “to” unit: 25 µm × 1 × 10-6 ÷ 0.001 = 0.025 mm.
1 micrometre in common units
| Unit | Value |
|---|---|
| Millimetres (mm) | 0.001 |
| Nanometres (nm) | 1000 |
| Metres (m) | 1 × 10-6 |
| Inches (in) | 3.937008 × 10-5 |
| Mils (mil) | 0.039370079 |
Micrometres conversion table
| Micrometres | mm | nm | m | in |
|---|---|---|---|---|
| 1 | 0.001 | 1000 | 1 × 10-6 | 3.937008 × 10-5 |
| 2.5 | 0.0025 | 2,500 | 2.5 × 10-6 | 9.84252 × 10-5 |
| 10 | 0.01 | 10,000 | 1 × 10-5 | 0.00039370079 |
| 25 | 0.025 | 25,000 | 2.5 × 10-5 | 0.00098425197 |
| 50 | 0.05 | 50,000 | 5 × 10-5 | 0.0019685039 |
| 100 | 0.1 | 100,000 | 1 × 10-4 | 0.0039370079 |
| 1,000 | 1 | 1,000,000 | 0.001 | 0.039370079 |
What is a micrometre?
A micrometre, usually called a micron, is one millionth of a metre. It measures fibres, cells, filter ratings, coatings and fine particles such as PM2.5 dust.
What is a millimetre?
A millimetre is one thousandth of a metre. Engineering drawings, construction plans, rainfall, screws, bolts and jewellery are all dimensioned in millimetres.
What is a nanometre?
A nanometre is one billionth of a metre. Wavelengths of light (visible light is roughly 380–750 nm), semiconductor features and molecules are measured in nanometres.
Common mistakes to avoid
Mixing the international foot (0.3048 m) with the old u.s. survey foot, confusing nautical and statute miles, and writing decimal feet such as 5.5 ft as “5 ft 5 in” (it is 5 ft 6 in).
Formula
1 µm = 0.001 mm1 µm = 1000 nm1 µm = 1 × 10^-6 m1 µm = 3.937008 × 10^-5 in1 µm = 0.039370079 milWorked example
Inputs — From: 25 µm.
Results — To = 0.025 mm; Nanometres = 25,000 nm; Metres = 0.000025 m; Inches = 0.00098425 in; Mils = 0.98425197 mil.
Frequently asked questions
How many microns in a millimetre?
1,000.
How many microns in a mil?
25.4.
What size are PM2.5 particles?
2.5 µm or smaller.
How do I change the units?
Pick any unit in the From and To menus. The value is converted in place, and the heading changes to show your conversion, for example “Micrometers to Millimeters Converter”.
Can I type into any field?
Yes. Every field is editable, so you can start from whichever unit you have.
How many units can I convert between?
27 length units, from the everyday to the specialised.
Which units are exact?
All factors here are exact by definition except astronomical and similar reference values, which use internationally agreed constants.
What formula does the Micrometer use?
1 µm = 0.001 mm.