Convert Micrometer to Mil
Convert micrometers to mils instantly. 1 micrometer = 0.0393700787 mil — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Mil to Micrometer converter for the reverse conversion.
Units explained
Micrometer
A micrometer (also called a micron) is a metric unit of length equal to one millionth of a meter (1×10⁻⁶ m). It is the standard unit for measuring microscopic dimensions in biology, materials science, and semiconductor manufacturing.
Defined alongside the meter when France adopted the metric system in 1795, using the SI prefix micro- (from Greek mikros, "small") to denote one-millionth.
Micrometers are used to measure cell sizes, bacteria, semiconductor process nodes, fiber diameters, dust particles, and wavelengths of infrared radiation. The diameter of a human hair is about 70 μm.
Defined in 1795 as part of the original French metric system; the name "micron" was officially deprecated by the BIPM in 1967 in favor of micrometer.
Mil
A mil (also called a thou) is an Imperial unit of length equal to one thousandth of an inch (1/1000 in = 0.0254 mm = 25.4 μm exactly). It is used in engineering, manufacturing, and materials specifications.
The mil is derived from the Latin mille, "thousand," denoting one-thousandth of an inch. Standardized in industrial use during the 19th-century rise of precision engineering.
Mils are used to specify thicknesses of plastic films, foils, paper, copper traces on printed circuit boards (PCBs), wire insulation, and paint coatings. A standard sheet of paper is about 4 mils thick.
Adopted in 19th-century engineering practice; the value (1/1000 in) became exact in 1959 when the inch was fixed at 25.4 mm via the International Yard and Pound Agreement. The British term is "thou"; American term is "mil".
Micrometer to Mil conversion formula
The relationship between micrometers and mils:
To convert micrometers to mils, multiply the value in micrometers by 0.0393700787. To reverse, multiply mils by 25.4.
How to use this converter
Type a value into the calculator. The result in mils updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Mil to Micrometer converter for the reverse direction.
Step-by-step: convert micrometers to mils
- Write down the value in micrometers (μm).
- Multiply that value by the factor 0.0393700787.
- The product is the equivalent value in mils (mil).
- To reverse, multiply the mil value by 25.4.
Worked examples
Example 1 — Convert 1 μm to mil:
1 × 0.0393700787 = 0.0393700787 mil
Example 2 — Convert 100 μm to mil:
100 × 0.0393700787 = 3.937007874 mil
Real-world example — Paper and film thicknesses
At the thickness of office paper (roughly 3 micrometers), converting between sub-millimeter units is routine for packaging and printing buyers comparing quotes from metric and US suppliers.
3 μm × 0.0393700787 = 0.1181102362 mil
Real-world example — Plastic-film thickness alternates
A 150-micrometer plastic film converts cleanly to mils — useful for packaging buyers reconciling supplier datasheets across metric and US measurement systems.
150 μm × 0.0393700787 = 5.905511811 mil
Real-world example — Hair-width scale measurements
A 70-micrometer measurement (about the diameter of a human hair) is the kind of value materials engineers regularly express in adjacent micro-scale units like mils for direct comparison across supplier datasheets.
70 μm × 0.0393700787 = 2.7559055118 mil
Micrometer to Mil conversion table
Standard reference values for converting micrometers to mils:
| Micrometer [μm] | Mil [mil] |
|---|---|
| 0.01 | 0.0003937008 |
| 0.1 | 0.0039370079 |
| 1 | 0.0393700787 |
| 2 | 0.0787401575 |
| 3 | 0.1181102362 |
| 4 | 0.157480315 |
| 5 | 0.1968503937 |
| 10 | 0.3937007874 |
| 20 | 0.7874015748 |
| 30 | 1.1811023622 |
| 40 | 1.5748031496 |
| 50 | 1.968503937 |
| 100 | 3.937007874 |
| 500 | 19.6850393701 |
| 1000 | 39.3700787402 |
Frequently asked questions
How many mils is 1 micrometer?
How do I convert micrometers to mils?
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How many mils is 100 micrometers?
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Sources & references
Conversion factor (1 μm = 0.0393700787 mil) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
- International Hydrographic Organization — Resolution on the Nautical Mile
International authority that standardised the nautical mile at exactly 1852 m in 1929 — the value adopted worldwide for sea and air navigation.