Enter a value in mils and click Convert to mm.
Quick values:
How to convert mils to millimeters
A mil is one-thousandth of an inch (0.001 in). It is commonly used for material thickness, wire coatings, plastic sheets, and manufacturing tolerances. This calculator converts mils to millimeters instantly using the exact conversion factor.
Formula: mm = mil × 0.0254
Since 1 inch equals 25.4 mm and 1 mil is 1/1000 inch, each mil is exactly 0.0254 mm.
Common mils to mm conversions
| Mils | Millimeters (mm) |
|---|---|
| 1 mil | 0.0254 mm |
| 2 mil | 0.0508 mm |
| 5 mil | 0.127 mm |
| 10 mil | 0.254 mm |
| 20 mil | 0.508 mm |
| 50 mil | 1.27 mm |
| 100 mil | 2.54 mm |
| 250 mil | 6.35 mm |
Where this conversion is used
- Electronics: PCB trace widths and spacing may be listed in mils.
- Coatings and films: Paint and protective film thickness is often given in mils.
- Engineering drawings: Older or US-based specs frequently use mil-based dimensions.
- Manufacturing: Tooling tolerances and shim stock can be specified in mils.
Step-by-step example
Convert 12 mil to mm
Use the formula: mm = mil × 0.0254
12 × 0.0254 = 0.3048 mm
So, 12 mil = 0.3048 mm.
Important: Do not confuse a mil (0.001 inch) with a millimeter (1/1000 meter). The words sound similar, but they represent different systems and different sizes.
Tips for accurate conversions
- Keep at least 3–4 decimal places for precision work.
- Use exact values when comparing tolerances in engineering specs.
- When reporting final dimensions, round only at the last step.
- Double-check units in datasheets: mil, mm, and inch are easy to mix up.
FAQ
Is 1 mil equal to 1 mm?
No. 1 mil equals 0.0254 mm. A millimeter is much larger than a mil.
How many mils are in 1 mm?
About 39.3701 mils. (Reverse formula: mil = mm ÷ 0.0254)
What is 100 mil in mm?
100 mil equals 2.54 mm.
Why do engineers still use mils?
Many standards, legacy drawings, and industry tools were created around inch-based dimensions. Mils remain convenient for very small inch-based measurements.