Convert mils (thousandths of an inch) to millimeters and back. Includes µm, cm, inches outputs, mil↔mm reference table, and metric drill/tap sizes.
In manufacturing and engineering, the mil (one thousandth of an inch) is prevalent across US-standard industries while the millimeter dominates international and scientific contexts. Converting between mil and mm is a daily task for PCB designers, coating engineers, machinists, and anyone working with mixed imperial-metric specifications in global supply chains.
This mil-to-mm calculator performs instant bidirectional conversion and simultaneously presents results in micrometers, centimeters, meters, and decimal inches. Preset buttons load common engineering values — from 1 mil precision coatings to 250 mil (¼″) sheet stock. A 15-row quick-reference table maps common mil values to mm, µm, and inches with typical application notes, and a collapsible metric drill/tap size table bridges the gap between metric fastener specs and imperial measurements.
Whether you are importing metric components for a US assembly, exporting US-spec coatings to metric markets, or just need a quick sanity check, this tool gives you every number in one place.
Mixed imperial-metric scenarios are everywhere: US-designed PCBs manufactured in Asia, European coatings applied in US factories, metric fasteners in imperial assemblies. This calculator bridges the gap instantly, with a reference table that eliminates repeated conversions for common thicknesses and drill sizes in day-to-day engineering and procurement work across design, quality, and manufacturing teams.
Mil to mm: mm = mil × 0.0254 | mm to Mil: mil = mm ÷ 0.0254. Also: 1 mil = 25.4 µm; 1 mm = 39.3701 mil.
Result: 62 mil = 1.5748 mm
62 mil × 0.0254 = 1.5748 mm. This is the standard FR4 PCB board thickness. In micrometers: 1,574.8 µm; in inches: 0.0620 in.
US manufacturing built its tooling, gaging, and documentation around the inch, using mils for small dimensions. International standards (ISO, IEC) use millimeters. As supply chains globalize, engineers must convert constantly. A PCB layout may specify 8 mil traces, but the Chinese fabricator needs 0.2032 mm on their process sheet. Both numbers must be exact.
A few key values appear repeatedly: 1 mil = 0.0254 mm (the exact factor); 10 mil = 0.254 mm (thin shim stock); 62 mil = 1.575 mm (standard PCB); 125 mil = 3.175 mm (⅛ inch); 250 mil = 6.35 mm (¼ inch). Memorizing these five lets you estimate most conversions without a calculator.
Metric taps are specified in mm, but US shops often think in mils when selecting drill bits. A 2.5 mm drill (for an M3 tap) is 98.4 mil — essentially "100 mil" for quick reference. The collapsible table in this calculator maps common metric drill sizes to their mil equivalents for fast shop-floor decisions.
Multiply by 0.0254. For example, 100 mil × 0.0254 = 2.54 mm.
Divide by 0.0254 (or multiply by 39.3701). For example, 1 mm ÷ 0.0254 ≈ 39.37 mil.
A mil is one thousandth of an inch (0.001 in). Also called a "thou" in British usage. It is not the same as a millimeter.
62 mil = 1.5748 mm. This is the standard thickness for most 4-layer FR4 circuit boards.
1 mil = 25.4 µm. Multiply mils by 25.4 to get micrometers.
No. A mil is 0.0254 mm — about 1/39 of a millimeter. They are different units in different measurement systems.