Mil to Inches Converter
Convert mils to inches and back. A mil is one thousandth of an inch, not a millimeter — enter mils (or switch to inches) to get inches, millimeters, and microns.
Example: with Value 20 · Direction Mils → Inches → Result: 0.02 in.
- In metric0.508 mm · 508 µm
- What a mil is1 mil = 0.001 in = 0.0254 mm (a thousandth of an inch, NOT a millimeter)
Computed by the calculator below using its default values. Change any input to see your own numbers.
1 mil = 0.001 inch, a thousandth of an inch (also called a thou). It is not a millimeter — a millimeter is nearly 40 times larger.
A thousandth of an inch, not a millimeter
In manufacturing and materials, a mil — sometimes called a thou — is one thousandth of an inch. Plastic film, coatings, foil, and circuit-board copper are all specified in mils. The math is trivial: divide mils by 1,000 for inches, multiply inches by 1,000 for mils.
The word causes trouble because it looks like millimeter. It is not. Ten mils is 0.254 mm, roughly a quarter of a millimeter. There is also an unrelated angular mil used in rifle scopes and gunnery, so context matters. When a spec sheet lists a thickness in mil, it means thousandths of an inch, which is what this converter uses.
How it’s calculated
inches = mils ÷ 1,000; mils = inches × 1,000. A mil (thou) is 0.001 inch. Metric outputs use 1 in = 25.4 mm exactly, so 1 mil = 0.0254 mm = 25.4 microns (µm).
Refers to the length mil, a thousandth of an inch, not the angular mil used in optics or the millimeter.
Mils to inches and metric
| Mils | Inches | Metric |
|---|---|---|
| 1 mil | 0.001 in | 0.0254 mm / 25.4 µm |
| 5 mil | 0.005 in | 0.127 mm / 127 µm |
| 10 mil | 0.010 in | 0.254 mm / 254 µm |
| 20 mil | 0.020 in | 0.508 mm / 508 µm |
| 60 mil | 0.060 in | 1.524 mm / 1,524 µm |
Computed as inches = mils ÷ 1,000; 1 mil = 0.0254 mm exactly, since 1 in = 25.4 mm.
Common mistakes
- Reading mil as millimeter — a 10 mil sheet is 0.254 mm, about a quarter of a millimeter, not 10 mm.
- Confusing the length mil with the angular mil used in scopes and artillery.
- Multiplying by 1,000 when converting mils to inches instead of dividing.
Frequently asked questions
How many inches is a mil?
One mil is 0.001 inch, a thousandth of an inch. So 20 mils is 0.020 inch.
Is a mil the same as a millimeter?
No, and this is the common trap. A mil is 0.001 inch, which is 0.0254 mm. A millimeter is almost 40 times larger than a mil.
How do I convert mils to inches?
Divide by 1,000. Mils ÷ 1,000 = inches; inches × 1,000 = mils.
What is a mil in millimeters or microns?
1 mil = 0.0254 mm = 25.4 microns (µm), because one inch is exactly 25.4 mm.