Mils to Millimeters Converter
Enter the length in mils below to convert it to millimeters.
Convert Mils to Millimeters
Enter a value in mils (mil) to convert to millimeters (mm).
Mils to Millimeters Conversion Chart (1–40 Continuous)
Continuous 1 to 40 mils lookup table with exact decimals and reduced nearest 1/64 fractions. Highlighted rows mark common shop and ruler values.
| Mils (mil) | Decimal (mm) | Fraction — Nearest 1/64 (Reduced) | Nearest 1/16 (Tape) |
|---|---|---|---|
1 mil★ Common | 0.0254 mm | 1/32 mm | 0 mm |
2 mil★ Common | 0.0508 mm | 3/64 mm | 1/16 mm |
3 mil★ Common | 0.0762 mm | 5/64 mm | 1/16 mm |
4 mil | 0.1016 mm | 7/64 mm | 1/8 mm |
5 mil★ Common | 0.127 mm | 1/8 mm | 1/8 mm |
6 mil★ Common | 0.1524 mm | 5/32 mm | 1/8 mm |
7 mil | 0.1778 mm | 11/64 mm | 3/16 mm |
8 mil★ Common | 0.2032 mm | 13/64 mm | 3/16 mm |
9 mil | 0.2286 mm | 15/64 mm | 1/4 mm |
10 mil★ Common | 0.254 mm | 1/4 mm | 1/4 mm |
11 mil | 0.2794 mm | 9/32 mm | 1/4 mm |
12 mil★ Common | 0.3048 mm | 5/16 mm | 5/16 mm |
How to Convert Mils to Millimeters
To convert mils to millimeters, multiply the length by the following conversion ratio: 0.0254 millimeters/mil.
Since one mil is equal to 0.0254 millimeters, you can use this simple formula to convert:
The length in millimeters is equal to the length in mils multiplied by 0.0254.
For example, here's how to convert 10 mils to millimeters using the formula above.
How Many Millimeters Are in a Mil?
There are 0.0254 millimeters in a mil, which is why we use this value in the formula above.
Our mil fraction and decimal calculator can convert mils and millimeters, and it automatically converts the results to US customary, imperial, and SI metric values.
Mils and millimeters are both units used to measure length. Keep reading to learn more about each unit.
How to Convert Mils to Fractional Inches (1/16″, 1/32″ & 1/64″)
Plain-language method for turning decimal inches into a standard tape-measure or machinist ruler fraction
Calculators give you a decimal number (such as 0.01 in), but tape measures and woodworking rulers are marked in binary fractions of an inch—most commonly 1/16″ on carpenter tapes, 1/32″ on fine woodworking rules, and 1/64″ on machinist scales.
Here is the step-by-step worked example for converting 10 mils (mil) into fractional inches:
- Find the decimal inches result: Convert 10 mil to inches to get 0.01 in.
- Separate the whole inches from the decimal part: Keep the whole number 0 aside, leaving the decimal remainder 0.01.
- Multiply the decimal part by your desired fraction denominator (16, 32, or 64) and round half up: Multiply 0.01 by 16, 32, or 64, then round to the nearest whole number (values ending in .5 round up).
- Reduce the fraction to lowest terms: If the rounded top number (numerator) is even, divide both top and bottom by 2 (or their Greatest Common Divisor) until the top number is odd, then combine with your whole inches.
What Is a Mil?
A mil is a unit of length equal to 0.0000254 meters (m), the base unit for length. One thousandth of an inch (0.001 in = 0.0254 mm), used in manufacturing tolerances and film thickness. [1]
The mil is classified as a US customary and imperial unit of length. Mils can be abbreviated as mil; for example, 1 mil can be written as 1 mil.
When working with mils (mil) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.
In practice, mils (mil) are widely used across fine-tolerance laboratory, analytical, and micro-scale length measurements within US customary and imperial workflows, engineering documentation, and technical data sheets.
What Is a Millimeter?
A millimeter is a metric unit of length equal to one-thousandth (1/1,000) of a meter or one-tenth (1/10) of a centimeter. By international definition, there are exactly 25.4 millimeters in one inch. [2]
The millimeter, or millimetre, is a standard SI metric unit of length. Millimeters can be abbreviated as mm; for example, 1 millimeter can be written as 1 mm.
In the metric system, "milli" is the prefix for thousandths, or 10⁻³. Millimeters are the default unit on mechanical engineering drawings and architectural blueprints worldwide.
Millimeters are commonly measured using metric steel rules, digital vernier calipers, depth gauges, and micrometers in CNC machining, 3D printing, automotive fasteners, and precision manufacturing.
When converting length between mils (mil) and millimeters (mm), keep full floating-point precision (1 mil = 0.0254 mm; 1 mm = 39.3700787 mil) during intermediate calculations and round only the final millimeter figure to match your instrument tolerance.
More Mil & Millimeter Conversions
Need to calculate in the opposite direction? Use our millimeters to mils converter (mm to mil) to switch your starting unit immediately. You can also explore related tools such as converting inches to millimeters, converting micrometers to millimeters, or converting centimeters to inches.
Frequently Asked Questions
References
- [1]NIST OWM StandardNIST OWM (SI Units — Length)·Length Metrology Standard — Mils (mil) to Millimeters (mm)
- [2]BIPM SpecificationBIPM (SI Base Unit: Metre (m))·Unit Specifications: Mil (Thou) (mil) & Millimeter (mm)
- [3]NIST HB 133 ReferenceNIST HB 133 (NIST Handbook 133 (2019 Ed.))·Conversion Factors & Mathematical Basis (mil to mm)