Mil to MM Converter: Mils, Millimeters, Microns and Gauge

Updated October 26, 2026mil, mm, microns, inches, gauge0.5 to 20 mil chart

One mil is one thousandth of an inch: 0.001 in, 0.0254 mm or 25.4 microns. To convert mil to mm, multiply by 0.0254. To convert mm to mil, multiply by 39.37. Plastic film is also sold by gauge, where 100 gauge equals 1 mil. Enter any thickness below, or use the charts for the poly bag, mailer, stretch film and sheeting thicknesses buyers ask about most.

4mil
0.1016millimeters
101.6microns
0.004inches
400gauge

4 mil is 0.1016 mm, 101.6 microns or 0.004 inch.

Mil to mm chart, with what each thickness is used for

The rows below cover the thicknesses that show up on poly bags, poly mailers, liners, stretch film and sheeting. The use column describes where each thickness is common, so you can sanity-check a spec before you order a case.

Mil to inches, millimeters, microns and gauge
Mil Inches Millimeters Microns Gauge Typical use
0.5 mil 0.0005 in 0.0127 mm 12.7 µm 5 ga Light HDPE can liners and produce bags
0.8 mil 0.0008 in 0.0203 mm 20.3 µm 8 ga 80 gauge hand stretch film for general pallet wrapping
1 mil 0.001 in 0.0254 mm 25.4 µm 1 ga Light-duty poly bags for small parts and light liners
1.5 mil 0.0015 in 0.0381 mm 38.1 µm 15 ga General-purpose poly bags and light trash liners
2 mil 0.002 in 0.0508 mm 50.8 µm 2 ga The standard poly bag: apparel, parts, kitting and food-contact bags
2.5 mil 0.0025 in 0.0635 mm 63.5 µm 25 ga Standard poly mailers for apparel and soft goods
3 mil 0.003 in 0.0762 mm 76.2 µm 3 ga Heavier poly bags and reclosable bags for hardware
4 mil 0.004 in 0.1016 mm 101.6 µm 4 ga Heavy-duty poly bags, reclosable bags for sharp parts and drop cloths
6 mil 0.006 in 0.1524 mm 152.4 µm 6 ga Heavy poly bags and construction or crawl space sheeting
8 mil 0.008 in 0.2032 mm 203.2 µm 8 ga Very heavy bags for dense or sharp loads
10 mil 0.01 in 0.254 mm 254 µm 1 ga Heavy sheeting and under-slab vapor retarders
12 mil 0.012 in 0.3048 mm 304.8 µm 12 ga  
15 mil 0.015 in 0.381 mm 381 µm 15 ga  
20 mil 0.02 in 0.508 mm 508 µm 2 ga  

How to convert mil to mm, and mm to mil

The conversions are exact because the inch is defined as 25.4 millimeters. A mil is a thousandth of that, so the math never changes:

  • mil to mm: multiply by 0.0254. 3 mil × 0.0254 = 0.0762 mm.
  • mm to mil: multiply by 39.37. 0.25 mm × 39.37 = 9.84 mil, close to 10 mil.
  • mil to microns: multiply by 25.4. 2 mil × 25.4 = 50.8 microns.
  • microns to mil: divide by 25.4. 20 microns ÷ 25.4 = 0.79 mil, which is 80 gauge stretch film.
  • gauge to mil: divide by 100. 120 gauge = 1.2 mil.

A mil is not a millimeter. One millimeter is 39.37 mil, so a bag listed as 4 mil is about a tenth of a millimeter thick. Mixing the two up is the most common thickness mistake on overseas spec sheets, where film is quoted in mm or microns and the same bag is sold in the US in mil.

Millimeters to mil

Millimeters to mil, microns and inches
Millimeters Mil Microns Inches
0.01 mm 0.39 mil 1 µm 0.0004 in
0.02 mm 0.79 mil 2 µm 0.0008 in
0.025 mm 0.98 mil 25 µm 0.001 in
0.03 mm 1.18 mil 3 µm 0.0012 in
0.04 mm 1.57 mil 4 µm 0.0016 in
0.05 mm 1.97 mil 5 µm 0.002 in
0.06 mm 2.36 mil 6 µm 0.0024 in
0.08 mm 3.15 mil 8 µm 0.0031 in
0.1 mm 3.94 mil 1 µm 0.0039 in
0.12 mm 4.72 mil 12 µm 0.0047 in
0.15 mm 5.91 mil 15 µm 0.0059 in
0.2 mm 7.87 mil 2 µm 0.0079 in
0.25 mm 9.84 mil 25 µm 0.0098 in
0.3 mm 11.81 mil 3 µm 0.0118 in
0.4 mm 15.75 mil 4 µm 0.0157 in
0.5 mm 19.69 mil 5 µm 0.0197 in
0.75 mm 29.53 mil 75 µm 0.0295 in
1 mm 39.37 mil 1 µm 0.0394 in

Microns to mil

Can liners made from high-density polyethylene are usually rated in microns, while low-density liners and most poly bags are rated in mil. A 16 micron HDPE liner is about 0.63 mil. HDPE is stiffer and stronger in tension, so a thin HDPE liner can lift a load that would need a much thicker low-density liner, though it tears more easily on sharp objects. Compare liners within the same resin, and use the trash can liner size chart for the sizing side.

Microns to mil, millimeters and gauge
Microns Mil Millimeters Gauge
8 µm 0.31 mil 0.008 mm 31 ga
10 µm 0.39 mil 0.01 mm 39 ga
12 µm 0.47 mil 0.012 mm 47 ga
13 µm 0.51 mil 0.013 mm 51 ga
15 µm 0.59 mil 0.015 mm 59 ga
16 µm 0.63 mil 0.016 mm 63 ga
17 µm 0.67 mil 0.017 mm 67 ga
20 µm 0.79 mil 0.02 mm 79 ga
23 µm 0.91 mil 0.023 mm 91 ga
25 µm 0.98 mil 0.025 mm 98 ga
30 µm 1.18 mil 0.03 mm 118 ga
38 µm 1.5 mil 0.038 mm 15 ga
50 µm 1.97 mil 0.05 mm 197 ga
64 µm 2.52 mil 0.064 mm 252 ga
76 µm 2.99 mil 0.076 mm 299 ga
100 µm 3.94 mil 0.1 mm 394 ga
127 µm 5 mil 0.127 mm 5 ga
150 µm 5.91 mil 0.15 mm 591 ga
200 µm 7.87 mil 0.2 mm 787 ga

Gauge to mil for stretch film and poly film

Film gauge is a plastics unit: 100 gauge is 1 mil, so 80 gauge hand stretch film is 0.8 mil or about 20 microns. Wire and sheet metal gauges run the other way, where a higher number means a thinner part, so never convert a film gauge with a metal gauge table. Some high-performance stretch films are labeled with an equivalent gauge, which rates its holding force against conventional film rather than its measured thickness. The stretch film gauge chart explains how to compare them.

Plastic film gauge to mil, microns and millimeters
Gauge Mil Microns Millimeters
50 gauge 0.5 mil 12.7 µm 0.0127 mm
60 gauge 0.6 mil 15.2 µm 0.0152 mm
63 gauge 0.63 mil 16 µm 0.016 mm
70 gauge 0.7 mil 17.8 µm 0.0178 mm
75 gauge 0.75 mil 19 µm 0.019 mm
80 gauge 0.8 mil 20.3 µm 0.0203 mm
90 gauge 0.9 mil 22.9 µm 0.0229 mm
100 gauge 1 mil 25.4 µm 0.0254 mm
120 gauge 1.2 mil 30.5 µm 0.0305 mm
150 gauge 1.5 mil 38.1 µm 0.0381 mm
200 gauge 2 mil 50.8 µm 0.0508 mm
250 gauge 2.5 mil 63.5 µm 0.0635 mm
300 gauge 3 mil 76.2 µm 0.0762 mm
400 gauge 4 mil 101.6 µm 0.1016 mm
600 gauge 6 mil 152.4 µm 0.1524 mm

4 mil vs 6 mil: how much thicker is it?

6 mil is 50 percent thicker than 4 mil: 0.1524 mm against 0.1016 mm, a difference of about 0.05 mm. In practice that buys puncture and tear resistance for sharp, heavy or abrasive contents, at the cost of more weight and less flexibility. For bags, step up when the contents have corners or edges that poke through 4 mil. For sheeting, the 6 mil vs 4 mil plastic sheeting comparison covers drop cloths, enclosures and crawl spaces.

What does a mil look like?

A sheet of standard copy paper is about 4 mil thick, so a 4 mil poly bag wall is roughly one sheet of paper. A payment card is 30 mil, or 0.76 mm, under the ISO/IEC 7810 ID-1 format. A 2 mil bag is half a sheet of paper and still strong enough for most apparel, parts and retail packaging, which is why it is the default thickness for flat and reclosable poly bags.

Shop poly bags and mailers by thickness

Frequently asked questions

How many mm is 1 mil?

One mil is exactly 0.0254 mm, because a mil is a thousandth of an inch and an inch is 25.4 mm.

Is a mil the same as a millimeter?

No. A millimeter is 39.37 mil. A 4 mil poly bag is about 0.1 mm thick, roughly a tenth of a millimeter.

How thick is 4 mil?

4 mil is 0.004 inch, 0.1016 mm or 101.6 microns, about the thickness of one sheet of copy paper.

How thick is 6 mil in mm?

6 mil is 0.1524 mm, or 152.4 microns. It is 50 percent thicker than 4 mil.

How many microns is 2 mil?

2 mil is 50.8 microns. Multiply mil by 25.4 to get microns.

What is 80 gauge in mil?

80 gauge is 0.8 mil, about 20 microns. In plastic film, 100 gauge equals 1 mil.

Which is thicker, 4 mil or 6 mil?

6 mil is thicker. It measures 0.006 inch against 0.004 inch for 4 mil, so it is 50 percent thicker.

How do I convert mm to mil?

Multiply millimeters by 39.37. For example, 0.1 mm is 3.94 mil and 0.25 mm is 9.84 mil.

Related tools and charts

Conversions use the exact definition 1 inch = 25.4 mm. Typical uses describe common practice and are not a substitute for a load test with your own contents.