Millimeters to Mils Converter
Enter the length in millimeters below to convert it to mils.
Convert Millimeters to Mils
Enter a value in millimeters (mm) to convert to mils (mil).
Millimeters to Mils Conversion Chart (1–40 Continuous)
Continuous 1 to 40 millimeters lookup table with exact decimals and reduced nearest 1/64 fractions. Highlighted rows mark common shop and ruler values.
| Millimeters (mm) | Decimal (mil) | Fraction — Nearest 1/64 (Reduced) | Nearest 1/16 (Tape) |
|---|---|---|---|
1 mm★ Common | 39.370079 mil | 39 3/8 mil | 39 3/8 mil |
2 mm★ Common | 78.740157 mil | 78 47/64 mil | 78 3/4 mil |
3 mm★ Common | 118.110236 mil | 118 7/64 mil | 118 1/8 mil |
4 mm | 157.480315 mil | 157 31/64 mil | 157 1/2 mil |
5 mm★ Common | 196.850394 mil | 196 27/32 mil | 196 7/8 mil |
6 mm★ Common | 236.220472 mil | 236 7/32 mil | 236 1/4 mil |
7 mm | 275.590551 mil | 275 19/32 mil | 275 9/16 mil |
8 mm★ Common | 314.96063 mil | 314 61/64 mil | 314 15/16 mil |
9 mm | 354.330709 mil | 354 21/64 mil | 354 5/16 mil |
10 mm★ Common | 393.700787 mil | 393 45/64 mil | 393 11/16 mil |
11 mm | 433.070866 mil | 433 5/64 mil | 433 1/16 mil |
12 mm★ Common | 472.440945 mil | 472 7/16 mil | 472 7/16 mil |
How to Convert Millimeters to Mils
To convert millimeters to mils, multiply the length by the following conversion ratio: 39.3700787 mils/millimeter.
Since one millimeter is equal to 39.3700787 mils, you can use this simple formula to convert:
The length in mils is equal to the length in millimeters multiplied by 39.3700787.
For example, here's how to convert 1 millimeters to mils using the formula above.
How Many Mils Are in a Millimeter?
There are 39.3700787 mils in a millimeter, which is why we use this value in the formula above.
Our millimeter fraction and decimal calculator can convert millimeters and mils, and it automatically converts the results to US customary, imperial, and SI metric values.
Millimeters and mils are both units used to measure length. Keep reading to learn more about each unit.
How to Convert Millimeters 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 0.03937 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 1 millimeters (mm) into fractional inches:
- Find the decimal inches result: Convert 1 mm to inches to get 0.03937 in.
- Separate the whole inches from the decimal part: Keep the whole number 0 aside, leaving the decimal remainder 0.03937.
- Multiply the decimal part by your desired fraction denominator (16, 32, or 64) and round half up: Multiply 0.03937 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 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. [1]
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.
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. [2]
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.
When converting length between millimeters (mm) and mils (mil), keep full floating-point precision (1 mm = 39.3700787 mil; 1 mil = 0.0254 mm) during intermediate calculations and round only the final mil figure to match your instrument tolerance.
More Millimeter & Mil Conversions
Need to calculate in the opposite direction? Use our mils to millimeters converter (mil to mm) to switch your starting unit immediately. You can also explore related tools such as converting millimeters to inches, converting millimeters to meters, or converting centimeters to inches.
Frequently Asked Questions
References
- [1]NIST OWM StandardNIST OWM (SI Units — Length)·Length Metrology Standard — Millimeters (mm) to Mils (mil)
- [2]BIPM SpecificationBIPM (SI Base Unit: Metre (m))·Unit Specifications: Millimeter (mm) & Mil (Thou) (mil)
- [3]NIST HB 133 ReferenceNIST HB 133 (NIST Handbook 133 (2019 Ed.))·Conversion Factors & Mathematical Basis (mm to mil)