Common medium plastic sheeting thickness.
Mils to mm Converter
Convert mil thickness to millimeters, inches, microns, and thou. Handy for plastic sheeting, films, liners, tape, labels, and quick questions like how thick is 40 mil plastic.
Convert thickness
Enter a thickness in mils, mm, inches, or microns. Results update instantly.
6 mil equals 0.1524 mm, 0.006 inch, and 152.4 microns.
Roll area helper
Estimate square feet and square meters from a rectangular sheet or roll.
1,000 sq ft
About 92.9 square meters.
Quick answer: how thick is 40 mil?
40 mil is 1.016 mm thick. It also equals 0.040 inch or 1,016 microns. In everyday terms, 40 mil is much thicker than standard plastic sheeting and is usually described as an extra-heavy liner or flexible sheet.
Mil thickness formula
A mil is one thousandth of an inch. To convert mils to millimeters, multiply by 0.0254.
- mm = mils × 0.0254
- mils = mm ÷ 0.0254
- microns = mils × 25.4
Where mils are used
Mils are common for plastic sheeting, vapor barriers, greenhouse film, pond liners, trash bags, tape, laminating film, and coatings. The word can also mean milliradians in optics, but this page is for thickness.
For product specs, compare both thickness and material type. Two sheets with the same mil rating can feel different if the plastic, reinforcement, or coating is different.
Common mil to mm chart
| Mils | Millimeters | Inches | Microns | Common note |
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Mils to mm FAQ
How thick is 10 mil in mm?
10 mil is 0.254 mm, 0.010 inch, or 254 microns.
How thick is 20 mil in mm?
20 mil is 0.508 mm, 0.020 inch, or 508 microns.
How thick is 40 mil?
40 mil is 1.016 mm, 0.040 inch, or 1,016 microns. It is a thick flexible sheet or liner compared with common 4 mil to 10 mil plastic sheeting.
Is 4 mil or 6 mil plastic thicker?
6 mil plastic is thicker. 4 mil is 0.1016 mm, while 6 mil is 0.1524 mm.