Convert microns (µm) to mils (thousandths of an inch) and back. Includes mm, inches, nm, and coating/PCB application reference table.
Microns (µm) and mils (thousandths of an inch, also called "thou") are the two dominant units for measuring small thicknesses in manufacturing — coatings, foils, films, PCB features, and precision machining tolerances. The conversion factor is 25.4: one mil equals exactly 25.4 micrometers in the international inch definition used by modern standards and production documentation across engineering teams and suppliers.
This micron-to-mil calculator provides instant bidirectional conversion, plus cross-conversions to millimeters, inches, nanometers, and centimeters. A bold result banner, visual bar, and six output cards show every relevant unit at a glance. Preset buttons load common values (1 mil, 5 mil, 100 µm), and a 12-row application reference table lists real-world coating, foil, and PCB thicknesses in both µm and mil.
Whether you are specifying conformal coatings, selecting solder-paste stencils, reading paint-gauge measurements, or designing flexible circuits, this tool gives you the exact number you need without manual division by 25.4.
Datasheets from US sources quote thicknesses in mils; metric sources use µm. Coating standards may specify both. Without a reliable converter, engineers spend time doing mental 25.4 arithmetic — and sometimes get it wrong. This calculator eliminates that friction and adds cross-references to mm, inches, and nm.
The application reference table is especially valuable: instead of just seeing "1.97 mil," you can immediately see that this matches conformal coating or automotive clear coat, confirming your value is in the right ballpark.
Micron to Mil: mil = µm ÷ 25.4 | Mil to Micron: µm = mil × 25.4. Related: 1 mil = 0.0254 mm = 0.001 inch; 1 µm = 1,000 nm.
Result: 1.969 mil
50 µm ÷ 25.4 = 1.969 mil. This is a typical conformal-coating thickness or automotive clear-coat layer.
Printed circuit board design straddles imperial and metric. Older US-based tools use mils for trace widths, pad sizes, and board thickness, while IPC standards and global manufacturers often specify in mm or µm. A standard PCB is 62 mil (1.6 mm) thick. Via drill sizes range from 8 to 20 mil (200–500 µm). Understanding both systems prevents costly fabrication errors.
Industrial coatings — paint, powder coat, anodize, electroplate — are specified in µm or mils depending on the standard. ISO 2808 describes thickness measurement methods in µm; ASTM D7091 uses mils. Cross-referencing both ensures you meet customer specs regardless of which standard they cite.
CNC machining tolerances for tight-fit components are often ±0.5 mil (±12.7 µm) or tighter. Surface roughness specs (Ra) range from 4 to 125 µin (0.1–3.2 µm). Being fluent in both micro-scale unit systems helps machinists communicate with both European and American clients.
One mil equals exactly 25.4 micrometers (µm). This is based on 1 mil = 0.001 inch and 1 inch = 25.4 mm.
A mil is one thousandth of an inch (0.001 in). It is also called a "thou" in British English. It is widely used in US manufacturing for thin dimensions.
No. A mil is 0.0254 mm (25.4 µm), while a millimeter is 1,000 µm. A millimeter is about 39.4 times larger than a mil.
One-ounce copper (per square foot) is approximately 1.38 mil (35 µm). This value is a common PCB fabrication baseline.
Typical conformal coating ranges from 1 to 5 mil (25–127 µm) depending on chemistry such as acrylic, urethane, silicone, or parylene. Always confirm the target range against the assembly standard and process capability.
Coating thickness can be measured with eddy-current gauges, magnetic gauges, micrometers, or cross-section microscopy. The best method depends on substrate type, coating material, and required measurement precision.