Mil to Millimeter Formula
mm = mil x 0.0254
Conversion factors follow SI relationships published by BIPM and NIST, where those standards apply.
Mil to Millimeter Converter
Quick Answer
1 mil = 0.0254 mm
Formula: Millimeter = Mil x 0.0254
Quick values
Worked examples
Convert 1 mil to mm
mm = 1 x 0.0254
Result: 1 mil = 0.0254 mm
Convert 10 mil to mm
mm = 10 x 0.0254
Result: 10 mil = 0.254 mm
Convert 100 mil to mm
mm = 100 x 0.0254
Result: 100 mil = 2.54 mm
About Mil and Millimeter
A mil is 0.001 inch (also called a thou). 1 mil = 0.0254 mm exactly because the international inch is 25.4 mm. PCB copper, paint, and plastic-film specs use mils; metric drawings use millimeters. There is no separate thou unit in the database — thou and mil are the same length.
Category hub: Length Conversion · Conversion charts · Conversion formulas
Mil to Millimeter Conversion Table
| Mil (mil) | Millimeter (mm) |
|---|---|
| 1 mil | 0.0254 mm |
| 2 mil | 0.0508 mm |
| 5 mil | 0.127 mm |
| 10 mil | 0.254 mm |
| 15 mil | 0.381 mm |
| 20 mil | 0.508 mm |
| 25 mil | 0.635 mm |
| 50 mil | 1.27 mm |
| 100 mil | 2.54 mm |
| 250 mil | 6.35 mm |
Browse all conversion charts → · Browse conversion formulas →
Practical use cases for Mil to Millimeter
PCB copper and solder mask
US fab notes still call copper and mask thickness in mils (or thou). Metric stackups and IPC metric tables need millimeters. 1 mil is 0.0254 mm exactly.
Paint, film, and foil
Coating DFT and plastic-film gauges are often 1–10 mil in North America and tens of microns or millimeters elsewhere. Converting avoids ordering the wrong roll.
Wire insulation and tubing
Heat-shrink and magnet-wire walls are quoted in mils on US catalogs and in mm on IEC sheets. Buyers convert before substituting a metric SKU.
Machining stock allowance
Shop travelers that say “leave 5 thou” must become 0.127 mm on a metric CNC setup. Thou and mil are the same 0.001 in.
Mil to Millimeter FAQs
Common questions about converting mil to millimeter.
How do you convert mils to millimeters?
Multiply mils by 0.0254. Example: 1 mil = 0.0254 mm, 10 mil = 0.254 mm, 39.37 mil ≈ 1 mm.
Is a mil the same as a thou?
Yes. Thou (thousandth of an inch) and mil are the same 0.001 in. This site stores the mil unit only; search “thou to mm” here.
Is a mil a millimeter?
No. A mil is 0.001 inch. A millimeter is 0.001 meter. 1 mm ≈ 39.37 mil. Confusing the two on a plating callout is a common drawing error.
Where does the mil to millimeter factor come from?
The 1959 international yard and pound agreement set 1 in = 25.4 mm exactly. One mil is 1/1,000 of that inch, so 0.0254 mm exactly. NIST documents the inch relationship.
Charts and printable PDF
Browse the conversion-chart library for printable mil / millimeter tables. PDF files are linked only when a matching download already exists.
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