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Try our mil conversion if you need quick help with the conversion of small lengths to this manageable measurement unit. In this short article, you'll learn:

  • What is a mil?
  • Conversion of mil to inches and other imperial measurement units.
  • Calculating the conversion of mil to the millimeter and other metric units.
  • And an example of the valuable micron to mil conversion.

What is a mil?

A mil is a small measurement unit for length in the metric system. The mil has usage similar to the micron in the metric system, primarily with applications in the science and technology sector in countries that use the imperial system for measurements.

A mil is defined exactly from the inch; in particular, we say that the mil is the thousandth part of an inch. We can write this first conversion in mathematical terms with the equation:

1 mil=0.001 in\footnotesize1\ \mathrm{mil} = 0.001 \ \mathrm{in}

Now that we know how much a mil is let's discover how to calculate the conversion from mil to other imperial units.

Calculating the conversion from mil to other imperial units

We already tackled the conversion from mil to inches, but we can still write the conversion factors:

  • To convert from mils to inches, multiply the measure by 0.0001 in/mil0.0001\ \mathrm{in/mil}.
  • To convert from inches to mils, multiply by the conversion factor 1000 mi/in1000\ \mathrm{mi/in}.

Once you know the conversion from mil to inches, the other conversions in the imperial system are relatively straightforward. As there are 1212 inches in a foot, we can write the conversion factor from mil to foot as:

1 mil=0.001 in12 in/ft=0.00008333 ft\footnotesize1\ \mathrm{mil} = \frac{0.001\ \mathrm{in}}{12\ \mathrm{in/ft}} = 0.00008333\ \mathrm{ft}

And so on, using the standard conversions between imperial units.

The conversion from mil to other measurement units: metric units

If you prefer to convert from mils to the metric system, you must first convert this unit to any other metric unit. We suggest starting from the micron, or micrometer, as it's the unit closest in magnitude to the mil.

1 mil=25.4 μm\footnotesize1\ \mathrm{mil} = 25.4\ \text{μm}

You only have to remember this number, as for every other conversion in the metric system, you can simply divide or multiply by powers of 1010. For example, if you want to calculate the conversion between a mil and millimeters, modify the previous equation:

1 mil=25.4 μm0.001 mm/μm=0.00254 mm\footnotesize \begin{split} 1\ \mathrm{mil} &= 25.4\ \text{μm} \cdot 0.001\ \text{mm/μm}\\ &= 0.00254\ \mathrm{mm} \end{split}

And so on!

Example of conversion from mil to micrometer

Take the highest-pitched string in a guitar. Let's say that the gauge of that string is 0.010 in0.010\ \mathrm{in}, a standard size for light gauge strings. First, let's convert this measurement into mils, as it will be much more manageable.

0.010 in0.010 in1,000 mil/in=10 mil\footnotesize \begin{split} 0.010\ \mathrm{in} &\equiv 0.010\ \mathrm{in}\cdot 1,\!000 \ \mathrm{mil/in}\\ & = 10\ \mathrm{mil} \end{split}

Apply now the conversion from mil to micrometer:

10 mil10 mil25.4 μ/mil=254 μm10\ \mathrm{mil} \equiv 10\ \mathrm{mil} \cdot 25.4\ \text{μ/mil} = 254\ \text{μm}

A fourth of a millimeter!


How do I convert inches to thou?

To convert inches to thou, follow these easy steps:

  1. Take a measurement in inches.
  2. Multiply the measurement by the conversion factor 1000 thou/in.
  3. That's it: as the thou is a much smaller unit than the inch, the magnitude of your measurement increased by multiple orders of magnitude.

How much is a mil?

A mil equals a thousandth of an inch. This small size makes the mil, or thou, ideal for scientific and technological applications. However, for most uses in international contexts or metric countries, it is preferred to use the micron, a smaller metric unit that operates at the same scale as the mil.

How much is 1 mm in mils?

1 mm equals exactly 39.37 mils. To calculate this conversion:

  1. Take the conversion from mil to micrometer: 1 mil = 25.4 μm.
  2. Find the conversion from mil to millimeter: 1 mil = 0.0254 mm.
  3. Compute the multiplicative inverse to find the conversion factor: 1 mm = 1/0.0245 mil = 39.37 mil.
Davide Borchia
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