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Mil to mm Conversion Calculator
Convert mils (thousandths of an inch) to millimeters and back. Includes µm, cm, inches outputs, mil↔mm reference table, and metric drill/tap sizes.
62.00 mil = 1.57 mm
Fraction of 1 inch (25.4 mm)
6.2% of 1 inch
Mils (thou)⧉
62.00
1 mil = 0.001 inch
Millimeters⧉
1.57
1 mm ≈ 39.37 mil
Micrometers (µm)⧉
1,574.80
1 µm = 0.001 mm
Inches⧉
0.06
1 inch = 1,000 mil = 25.4 mm
Centimeters⧉
0.16
1 cm = 10 mm
Meters⧉
0.00
1 m = 1,000 mm
Mil ↔ Millimeter Quick-Reference
| Mil | mm | µm | Inches | Typical Use |
|---|---|---|---|---|
| 0.50 | 0.01 | 12.70 | 0.00 | Thin film |
| 1.00 | 0.03 | 25.40 | 0.00 | Precision coating |
| 2.00 | 0.05 | 50.80 | 0.00 | PCB copper (1 oz) |
| 5.00 | 0.13 | 127.00 | 0.01 | Solder mask |
| 10.00 | 0.25 | 254.00 | 0.01 | Thin shim |
| 20.00 | 0.51 | 508.00 | 0.02 | Heavy coating |
| 31.00 | 0.79 | 787.40 | 0.03 | PCB (0.031″) |
| 62.00 | 1.57 | 1,574.80 | 0.06 | Standard PCB |
| 100.00 | 2.54 | 2,540.00 | 0.10 | 10 AWG radius |
| 125.00 | 3.18 | 3,175.00 | 0.13 | ⅛ inch |
| 250.00 | 6.35 | 6,350.00 | 0.25 | ¼ inch |
| 375.00 | 9.53 | 9,525.00 | 0.38 | ⅜ inch |
| 500.00 | 12.70 | 12,700.00 | 0.50 | ½ inch |
| 750.00 | 19.05 | 19,050.00 | 0.75 | ¾ inch |
| 1,000.00 | 25.40 | 25,400.00 | 1.00 | 1 inch |
Metric Drill / Tap Sizes → Mils
| mm | Mil | Inches | Typical Use |
|---|---|---|---|
| 0.3 | 11.81 | 0.01 | PCB via |
| 0.5 | 19.69 | 0.02 | Watch screw |
| 1 | 39.37 | 0.04 | PCB through-hole |
| 1.5 | 59.06 | 0.06 | M1.6 clearance |
| 2 | 78.74 | 0.08 | M2 clearance |
| 2.5 | 98.43 | 0.10 | M3 tap |
| 3.3 | 129.92 | 0.13 | M4 tap |
| 4.2 | 165.35 | 0.17 | M5 tap |
| 5 | 196.85 | 0.20 | M6 tap |
| 6.8 | 267.72 | 0.27 | M8 tap |
| 8.5 | 334.65 | 0.33 | M10 tap |
| 10.2 | 401.57 | 0.40 | M12 tap |
Planning notes, formulas, and examples
About the Mil to mm Conversion Calculator
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 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, the page keeps the surrounding unit systems and drill-size references together.
When This Page Helps
Mixed imperial-metric scenarios are everywhere: US-designed PCBs manufactured in Asia, European coatings applied in US factories, metric fasteners in imperial assemblies. Keeping the common thicknesses, unit conversions, and drill-size references together cuts down repeated conversions in day-to-day engineering and procurement work across design, quality, and manufacturing teams.
How to Use the Inputs
- Choose "Mils → Millimeters" or "Millimeters → Mils" from the direction selector.
- Type the value to convert in the input field.
- Adjust decimal precision (0–10 places) for your accuracy needs.
- Click any preset button to load a common conversion.
- Read the primary result in the bold banner, then review six unit output cards.
- Scroll to the reference table for standard mil ↔ mm equivalences.
- Expand the metric drill/tap table for machining cross-reference.
Formula used
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.Example Calculation
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.
Tips & Best Practices
- Quick mental shortcut: 1 mil ≈ 25 µm, so 10 mil ≈ 0.25 mm — close enough for rough estimates.
- PCB trace widths are typically spec'd in mil (e.g., 6 mil, 8 mil, 10 mil) but metric fabs may want mm.
- For 3-decimal-place mm results, 4-digit precision in the calculator is enough.
- The reference table covers the most-requested values — bookmark this page for shop-floor use.
- When ordering metric drill bits to match mil specs, round to the nearest standard metric size.
- Use 6+ decimal places when working with thin-film deposition or semiconductor processes.
Why Mil and mm Coexist
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.
Common Mil-mm Equivalences Every Engineer Should Know
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 Drill and Tap Sizes
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.
Sources & Methodology
Last updated:
Frequently Asked Questions
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.
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