What Is a Mil? Poly Bag & Plastic Film Thickness, Explained

Updated October 12, 2026mil, micron, mm, gaugeExact conversions

A mil is one thousandth of an inch: 0.001 in, 25.4 microns or 0.0254 mm. Poly bags, plastic sheeting and tape are sold by the mil in the US. A mil is not a millimeter. One millimeter is 39.37 mil, so a 2 mil bag is about 0.05 mm thick.

Common film thicknesses in four units
Mil Inches Millimeters Microns (µm) Gauge
1 0.001 0.0254 25.4 100
1.5 0.0015 0.0381 38.1 150
2 0.002 0.0508 50.8 200
3 0.003 0.0762 76.2 300
4 0.004 0.1016 101.6 400
6 0.006 0.1524 152.4 600

Formulas: mil x 25.4 = microns. Microns / 25.4 = mil. mil x 0.0254 = mm. mm x 39.37 = mil. Gauge / 100 = mil.

Mil thickness chart

Every poly bag, sheeting roll and stretch film spec in the US uses mil. Too thin and the bag tears at the seam in transit. Too thick and you pay for film the job does not need.

Mil Inches Millimeters Feels like Typical uses
1 mil 0.001" 0.025 mm Produce-bag film Lightweight liners, short-term dust covers
1.5 mil 0.0015" 0.038 mm Bread bag Light parts, apparel, single-use packaging
2 mil 0.002" 0.051 mm Standard poly bag General purpose: parts, documents, retail goods
3 mil 0.003" 0.076 mm Heavy freezer bag Hardware, moderately sharp parts, food storage
4 mil 0.004" 0.102 mm Thick, semi-rigid Industrial parts, metal components, bulk storage
6 mil 0.006" 0.152 mm Tarp-like Sharp or heavy parts, construction, long-term storage
8 to 10 mil 0.008 to 0.010" 0.20 to 0.25 mm Rigid sheet Heavy containment, abrasive contents

Mil to micron, millimeter, inch and gauge: 0.5 to 10 mil

Mil, micron, millimeter and gauge are four ways of writing the same film thickness. North America sells film by the mil. Most other countries use microns, one thousandth of a millimeter. Stretch and shrink film use gauge, which is mil x 100. All four trace back to the inch: 1 mil = 0.001 in = 0.0254 mm = 25.4 µm = 100 gauge.

Mil Inches Millimeters Microns (µm) Gauge
0.5 0.0005 0.0127 12.7 50
0.6 0.0006 0.0152 15.2 60
0.7 0.0007 0.0178 17.8 70
0.75 0.00075 0.0190 19.0 75
0.8 0.0008 0.0203 20.3 80
0.9 0.0009 0.0229 22.9 90
1 0.001 0.0254 25.4 100
1.1 0.0011 0.0279 27.9 110
1.25 0.00125 0.0318 31.8 125
1.5 0.0015 0.0381 38.1 150
1.75 0.00175 0.0444 44.4 175
2 0.002 0.0508 50.8 200
2.25 0.00225 0.0572 57.2 225
2.5 0.0025 0.0635 63.5 250
3 0.003 0.0762 76.2 300
3.5 0.0035 0.0889 88.9 350
4 0.004 0.1016 101.6 400
4.5 0.0045 0.1143 114.3 450
5 0.005 0.1270 127.0 500
6 0.006 0.1524 152.4 600
7 0.007 0.1778 177.8 700
8 0.008 0.2032 203.2 800
10 0.01 0.2540 254.0 1000

Millimeters and microns to mil

Multiply millimeters by 39.37, or divide microns by 25.4. 0.25 mm is 9.84 mil, 0.05 mm is 1.97 mil and 0.025 mm is 0.98 mil. A spec sheet that says 50 µm means about 2 mil.

Millimeters Microns (µm) Mil
0.01 10 0.39
0.0125 12.5 0.49
0.015 15 0.59
0.02 20 0.79
0.025 25 0.98
0.03 30 1.18
0.035 35 1.38
0.04 40 1.57
0.05 50 1.97
0.06 60 2.36
0.075 75 2.95
0.08 80 3.15
0.1 100 3.94
0.125 125 4.92
0.15 150 5.91
0.2 200 7.87
0.25 250 9.84
0.3 300 11.81
0.5 500 19.69
1 1000 39.37

Stretch and shrink film gauge to mil and micron

Stretch film is labeled in gauge. 80 gauge is the standard hand wrap. 60 and 70 gauge are economy or pre-stretched films. 90 to 120 gauge are for heavy or sharp loads. Pre-stretched film is thinner on the roll, often 38 to 47 gauge, because it was stretched at the factory and is rated by load performance. Shrink film is quoted the same way. 60 and 75 gauge polyolefin are the common retail wraps. The stretch film gauge chart maps each gauge to a load weight.

Gauge Mil Microns Millimeters
38 0.38 9.7 0.0097
47 0.47 11.9 0.0119
50 0.5 12.7 0.0127
60 0.6 15.2 0.0152
63 0.63 16.0 0.0160
70 0.7 17.8 0.0178
75 0.75 19.0 0.0190
80 0.8 20.3 0.0203
90 0.9 22.9 0.0229
100 1 25.4 0.0254
120 1.2 30.5 0.0305
150 1.5 38.1 0.0381
200 2 50.8 0.0508

What each thickness is used for

Thicker film resists punctures and tears better, and it also costs and weighs more per bag. Pick the thinnest film that survives the contents and the trip. The examples link to stocked products in each band.

Thickness Microns Typical packaging use Stocked examples
0.5 to 0.8 mil 13 to 20 Garment bags, produce bags, light can liners, sandwich bags 0.6 mil garment bags, 0.4 to 0.9 mil can liners
1 mil 25 Light poly bags for dry goods, pallet top sheets, dust covers, light pallet covers 1 mil poly sheeting, 1 mil pallet covers
1.5 mil 38 Standard flat and gusseted poly bags, poly tubing, recycling liners 1.5 mil poly bags, 1.5 mil poly tubing
1.6 to 1.9 mil 41 to 48 Economy and standard acrylic carton sealing tape, film plus adhesive 1.6 mil acrylic tape, 3M 371 at 1.9 mil
2 mil 51 The default poly bag and reclosable bag thickness, 2 mil pallet covers, poly tubing 2 mil reclosable bags, 2 mil flat poly bags
2.2 to 2.5 mil 56 to 64 Heavy duty carton sealing tape, surface protection film 3M 373 at 2.5 mil, carton sealing tape
3 mil 76 UV amber bags, heavier reclosable bags, pallet covers for outdoor storage, barricade tape 3 mil UV bags, 3 mil pallet covers
3.1 mil 79 Static shielding bags for circuit boards 3.1 mil static shielding bags
4 mil 102 Heavy poly bags for parts and hardware, 4 mil sheeting, 4 mil poly tubing, machinery covers 4 mil poly bags, 4 mil reclosable bags, 4 mil black sheeting
4.9 to 6 mil 124 to 152 Masking tape, duct tape, vinyl safety tape, 6 mil heavy duty bags and sheeting 4.9 to 6 mil masking tape, 6 mil reclosable bags, 6 mil poly bags
7 to 8 mil 178 to 203 Reinforced water activated tape, filament tape, 8 mil heavy flat poly bags 7 mil reinforced kraft tape, 8 mil flat poly bags
10 mil and up 254 and up Gaffers tape, VHB bonding tape, anti-slip tape, floor marking tape 11 mil gaffers tape, floor marking and anti-slip tape

How to choose a mil thickness

Match the thickness to the failure you want to prevent. Tearing on sharp edges calls for 4 to 6 mil. Dust and moisture protection needs 1 to 2 mil. Goods shipped loose inside a carton usually land at 2 to 3 mil. Doubling the mil roughly doubles the film in the wall and the cost, so a heavier bag than the job needs adds cost at case quantities. When two thicknesses both work, compare the price per bag at your case count.

  • Soft, light, no corners: 1 to 1.5 mil. Apparel, paper goods, food service items.
  • Everyday parts and retail goods: 2 mil. It seals well on an impulse sealer and resists tearing on a pick line.
  • Metal parts, hardware, anything with an edge: 4 mil. Below that, corners poke through during handling.
  • Sharp, heavy or stored outdoors: 6 mil and up. Castings, bulk fasteners, long-term storage under UV.
  • Electronics: the material matters more than the thickness. Use 3.1 mil static shielding or pink anti-static film. The anti-static vs regular bag guide covers the difference.
  • Carton sealing tape: 1.6 to 1.9 mil for light single wall cartons, 2.2 to 2.5 mil for heavier or recycled-content board, 3 mil and up for double wall or cold storage. See the tape mil thickness guide.

Which is thicker: 2 mil or 3 mil, 4 mil or 6 mil?

A higher mil number is always thicker film. 3 mil is 50 percent thicker than 2 mil. 4 mil is twice as thick as 2 mil. 6 mil is 50 percent thicker than 4 mil.

Comparison Difference Microns
1 mil vs 2 mil 2 mil is twice as thick 25.4 vs 50.8
1.5 mil vs 2 mil 2 mil is 33 percent thicker 38.1 vs 50.8
2 mil vs 3 mil 3 mil is 50 percent thicker 50.8 vs 76.2
2 mil vs 4 mil 4 mil is twice as thick 50.8 vs 101.6
2 mil vs 6 mil 6 mil is three times as thick 50.8 vs 152.4
4 mil vs 6 mil 6 mil is 50 percent thicker 101.6 vs 152.4

For poly bags compared size by size, see 2 mil vs 4 mil poly bags. For sheeting, see 6 mil vs 4 mil plastic sheeting.

Buy these sizes by the case

Each collection lists the mil and the case count on every size. The listed price is for the whole case.

Reclosable poly bagsFlat and gusseted poly bagsPoly tubingStretch film

Orders of one or two items with a product subtotal of $500 or more ship free when the checkout freight rate is $45 or less, or $90 or less on orders of $1,000 or more. Orders of three or more items get the volume discount instead of free shipping. See the shipping policy.

Frequently asked questions

Is a mil the same as a millimeter?

No. A mil is one thousandth of an inch, 0.001 in. A millimeter is about 39 mil, so a bag sold as 2 mm would be nearly 80 mil thick.

How many microns is 1 mil?

25.4 microns. One mil is one thousandth of an inch, and an inch is 25.4 millimeters, so a mil is exactly 25.4 micrometers.

How thick is 1.5 mil?

0.0015 inch, which is 38.1 microns or 0.0381 mm. It is a common thickness for light flat and gusseted poly bags and poly tubing.

What is 2 mil in mm?

0.0508 mm, a little over one twentieth of a millimeter. 2 mil is also 50.8 microns and 200 gauge.

Is 6 mil thicker than 4 mil?

Yes. 6 mil is 0.006 inch, or 152 microns. 4 mil is 0.004 inch, or 102 microns. 6 mil is 50 percent thicker, and a larger mil number always means thicker film.

How do I convert gauge to mil?

Divide gauge by 100. 80 gauge stretch film is 0.8 mil, about 20 microns. To go from gauge to microns, multiply by 0.254.

What thickness is 100 micron plastic in mil?

About 4 mil. 100 divided by 25.4 is 3.94, so film sold as 4 mil in the US matches 100 micron film sold elsewhere.

What mil poly bag do I need for shipping?

For most products shipped inside a carton, 2 mil protects against dust, moisture and scuffing. Step up to 4 mil for hardware and edged parts, and to 6 mil for heavy or abrasive contents.

How do I measure the mil of a bag I already have?

Use a micrometer on a single wall, not a folded edge, and read thousandths of an inch. Compare it with the nominal mil on the product page before you reorder.

Related references

Reference values: 1 inch = 25.4 mm by definition, the international inch of 1959. Plastic film gauge is defined as 100 gauge = 1 mil. It is unrelated to wire gauge or sheet metal gauge.