Mil to Inch Conversion Calculator — Thou to Inches
A mil (also called a thou) is one thousandth of an inch. Convert any number of mils to decimal inches, fractional inches (nearest 1/64), feet, millimeters and micrometers — used in PCB design, coating thickness and precision manufacturing.
mil
Exact conversion: 1 mil = 0.001 inch
- 1
Conversion factor
1 mil = 1 ÷ 1,000 in = 0.001A mil (thou) is defined as exactly one thousandth of an inch. - 2
Convert mils to inches
50 × 0.001 = 0.050000
How does this calculator work?
Multiply mils by 0.001 to get inches: 1 mil = 0.001 in, 100 mils = 0.1 in, 1000 mils = 1 in. The conversion is exact because 1 mil is defined as 1/1000 of an inch. Common in PCB design (e.g. 6 mil trace = 0.006 in = 0.152 mm) and coating thickness measurement.
Formula
How this is calculated
The mil (short for milli-inch, also called a thou in British English) is a unit of length defined as exactly one thousandth of an inch. Because 1 inch = 25.4 mm exactly, all conversions from mils are exact: 1 mil = 0.001 in = 0.0254 mm = 25.4 µm. Multiplying by 0.001 converts mils to inches, and dividing by 12 further converts inches to feet.
Mils are the standard unit for PCB (printed-circuit board) trace widths and clearances in North American design tools — a 6 mil trace is 0.006 in wide, or about 0.152 mm. Paint and powder-coat thickness gauges in the US read in mils, as do wire and metal-foil gauges in many manufacturing contexts. Elsewhere, micrometers (µm) or millimeters serve the same role.
This calculator also shows the nearest fractional inch to the nearest 1/64 for users who need to communicate dimensions in the fractional format common on US mechanical drawings. To convert in the reverse direction — from inches to mils — multiply the inch value by 1000.
Frequently asked questions
Exactly 1000 mils equal 1 inch, because 1 mil is defined as 1/1000 of an inch. So 1 in = 1000 mil, and 0.001 in = 1 mil.
No. A mil (thou) is 0.001 inch = 0.0254 mm. A millimeter is much larger — 1 mm ≈ 39.37 mils. The abbreviation "mil" can cause confusion; in measurement, always verify whether the context means mil (1/1000 inch) or millimeter.
PCB designers specify trace widths and via drill sizes in mils (e.g. 6 mil trace = 0.006 in). Industrial coating inspectors measure film thickness in mils. Sheet metal gauges and wire diameters in the US are often expressed in mils. The calculation is also needed when reading legacy engineering drawings.
Also known as
TG we-Calculate Editorial Team. (2026). Mil to Inch Conversion Calculator — Thou to Inches [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/mil-to-inch-conversion-calculator
TG we-Calculate Editorial Team. "Mil to Inch Conversion Calculator — Thou to Inches." TG we-Calculate. 2026. https://we-calculate.com/calculator/mil-to-inch-conversion-calculator.
TG we-Calculate Editorial Team, "Mil to Inch Conversion Calculator — Thou to Inches," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/mil-to-inch-conversion-calculator
@misc{wecalculate_mil_to_inch_conversion_calculator, title = {Mil to Inch Conversion Calculator — Thou to Inches}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/mil-to-inch-conversion-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?