# Micron to Mil Converter URL: https://speedycalculator.com/calculators/conversion/micron-to-mil/ Last updated: 2026-10-25 > Convert micrometres (µm) to mils (mil): 1 micrometre = 0.039370079 mil, so multiply by 0.039370079 or divide by 25.4. Both fields are editable, so you can also type in mils and get micrometres back. ## Inputs - Micrometres (µm) ## Results - Mils ## Formula ``` 1 µm = 0.039370079 mil 1 mil = 25.4 µm mil = µm × 0.039370079 ``` ## Explanation A mil (one thousandth of an inch) is exactly 25.4 µm. Coating, film and gasket thicknesses are quoted in microns in metric specs and in mils in U.S. specs. ### How to use the Micron to Mil Converter - Type the number of micrometres into the **Micrometres** field. Decimals such as 12.7 are fine. - Read the answer in **Mils** – it updates as you type, with no button to press. - To convert the other way, type into **Mils** and the micrometres are recalculated. - Press **Copy results** to copy both values with the page title, or **Copy link** to share this exact conversion. This page converts only µm ⇄ mil. Need a different unit? Use the general length converter, where you can choose any “from” and “to” unit. ### How it works Both units measure length, so they are always in the same ratio: one micrometre equals 0.039370079 mils. The calculator multiplies the number of micrometres you type by 0.039370079 to give mils, and when you type into the mils field it divides by the same factor to give micrometres. Because the ratio never changes, doubling the micrometres always doubles the mils. Results are calculated at full precision and rounded only for display (up to eight decimal places, with very large or small values shown in scientific notation). ### How to convert micrometres to mils - Write down the value in micrometres, for example **25.4 µm**. - Multiply by the conversion factor 0.039370079 (because 1 micrometre = 0.039370079 mil). - 25.4 × 0.039370079 = **1 mil**. - To go back from mils to micrometres, divide by 0.039370079 – or multiply by 25.4. ### µm to mil conversion table MicrometresMilsMilsMicrometres1 µm0.039370079 mil1 mil25.4 µm5 µm0.19685039 mil2 mil50.8 µm10 µm0.39370079 mil5 mil127 µm25 µm0.98425197 mil10 mil254 µm25.4 µm1 mil20 mil508 µm50 µm1.9685039 mil50 mil1,270 µm75 µm2.9527559 mil100 mil2,540 µm100 µm3.9370079 mil1,000 mil25,400 µm150 µm5.9055118 mil200 µm7.8740157 mil250 µm9.8425197 mil500 µm19.685039 mil ### 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 mil? A mil (or thou) is one thousandth of an inch, 25.4 µm. It is used in North America for plastic film, garbage bags, paint and coating thickness and circuit-board traces; it is not a millimetre. ### Quick mental conversion For a fast estimate, multiply micrometres by about **0.039** to get mils; the error is about 0.9%. Use the calculator above when you need the exact figure. ### 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). ## Worked example Inputs — Micrometres: 25.4 µm. Results — **Mils = 1 mil**. ## FAQ **How many microns is 1 mil?** 25.4 µm. **How many mils is 100 µm?** About 3.94 mil. **How do I convert micrometres to mils?** Multiply the number of micrometres by 0.039370079. For example, 25.4 µm × 0.039370079 = 1 mil. **How do I convert mils back to micrometres?** Divide by 0.039370079 (or multiply by 25.4), or simply type the value into the mils field above. **What is 10 µm in mils?** 10 µm = 0.39370079 mil. **What is 100 µm in mils?** 100 µm = 3.9370079 mil. **Is this conversion exact?** Yes. The factor comes from the official definitions of both units (NIST and the SI), so the only difference you may see is rounding in the last displayed digit. **Can I convert to other units on this page?** This page converts only between micrometres and mils. To pick any length unit, use the general length converter linked under Related calculators. **What formula does the Micron to Mil Converter use?** 1 µm = 0.039370079 mil. ## Sources - [NIST Special Publication 811 – Guide for the Use of the International System of Units](https://www.nist.gov/pml/special-publication-811) - [NIST Handbook 44 Appendix C – General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)