Poly bag thickness is measured in mil in the US and in microns (µm) almost everywhere else. One mil is one thousandth of an inch, which equals 25.4 microns. Gauge is a third unit used in the US film trade: 100 gauge = 1 mil. So a 2 mil bag is 50.8 µm, or 200 gauge.
We quote in both units every day at Hanpak, because a buyer in Texas and a buyer in Rotterdam can order the same bag and describe it with different numbers. Here is how the units work, a conversion chart, and how to pick a thickness.
The three units in one minute
- Mil = 0.001 inch. Used by US retailers, distributors and most US spec sheets. Not to be confused with millimeter.
- Micron (µm, “mic”) = 0.001 millimeter. Used in Europe, Asia, Africa and by most factories, including ours.
- Gauge = 0.01 mil in the US film trade. 100 gauge = 1 mil. In the UK, polythene gauge is roughly micron x 4, so 500 gauge polythene is about 125 µm. Close to the US figure, but check which one a supplier means.
Conversion formulas
- mil x 25.4 = microns
- microns ÷ 25.4 = mil (or microns x 0.0394)
- mil x 100 = gauge (US)
- microns x 4 ≈ gauge
- microns ÷ 1,000 = millimeters
Mil to micron conversion chart
| Mil | Inches | Microns (µm) | Gauge (US) | Typical bag |
|---|---|---|---|---|
| 0.3 | 0.0003 | 7.6 | 30 | Thinnest HDPE produce and liner film |
| 0.4 | 0.0004 | 10.2 | 40 | HDPE produce bags on roll |
| 0.5 | 0.0005 | 12.7 | 50 | HDPE T-shirt grocery bags, light can liners |
| 0.7 | 0.0007 | 17.8 | 70 | Heavier HDPE T-shirt bags, light LDPE trash bags |
| 1.0 | 0.001 | 25.4 | 100 | Light flat poly bags, bread bags, kitchen trash bags |
| 1.5 | 0.0015 | 38.1 | 150 | Newspaper bags, OPP cello bags, retail bags |
| 2.0 | 0.002 | 50.8 | 200 | The most common flat poly bag: parts, clothing, food |
| 2.5 | 0.0025 | 63.5 | 250 | Mailers, heavier zipper bags |
| 3.0 | 0.003 | 76.2 | 300 | Contractor bags, hardware packing |
| 4.0 | 0.004 | 101.6 | 400 | Industrial parts and tools, heavy liners |
| 6.0 | 0.006 | 152.4 | 600 | Poly sheeting, pallet covers, puncture-prone loads |
| 8.0 | 0.008 | 203.2 | 800 | Extra-heavy bags and sheeting |
| 10.0 | 0.010 | 254 | 1,000 | Heavy construction sheeting |
Micron to mil conversion chart
| Microns (µm) | Mil | Microns (µm) | Mil |
|---|---|---|---|
| 8 | 0.31 | 35 | 1.38 |
| 10 | 0.39 | 40 | 1.57 |
| 12 | 0.47 | 50 | 1.97 |
| 15 | 0.59 | 60 | 2.36 |
| 18 | 0.71 | 75 | 2.95 |
| 20 | 0.79 | 100 | 3.94 |
| 25 | 0.98 | 150 | 5.91 |
| 30 | 1.18 | 200 | 7.87 |
Round to two decimals on a spec sheet. Writing “2 mil (50 µm)” is normal trade practice and close enough for ordering.
Why the same thickness doesn’t mean the same strength
This is where most first-time buyers get caught. Mil or micron tells you how thick the film is. It does not tell you how strong the bag is. The resin matters as much as the number.
- HDPE is stiff and very strong for its weight. A 13 µm (0.5 mil) HDPE T-shirt bag carries groceries. That is why HDPE bags and can liners are usually sold in microns: the numbers are small.
- LDPE and LLDPE are softer and stretch before they tear. They need more thickness to carry the same weight, but they resist punctures far better. LLDPE trash bags are usually sold in mil.
So a 16 µm HDPE can liner and a 0.9 mil (23 µm) LLDPE liner can both be the right bag for a 33-gallon can. The HDPE one is cheaper and handles paper and wet waste. The LLDPE one is better for anything with sharp corners. Compare bags within one resin, never mil against micron across resins.
From our own production: the thinnest film we would put into a working bag is about 8 µm (0.3 mil) for HDPE and 20 µm (0.8 mil) for LDPE. Below that, quality becomes hard to hold.
Popular thickness by bag type and market
| Bag type | Common in the US | Notes |
|---|---|---|
| HDPE T-shirt grocery bags | 0.5–0.7 mil (13–18 µm) | EU buyers often order 35–50 µm; bags under 50 µm count as lightweight carrier bags under EU rules |
| HDPE produce bags on roll | About 0.3–0.5 mil (8–13 µm) | Thin, crisp, easy to tear off the roll |
| High-density can liners | 6–24 µm | Sold in microns |
| Low-density household trash bags | 0.7–1.0 mil (18–25 µm) | Sold in mil |
| Contractor bags | 3 mil (76 µm) and up | Construction debris, sharp waste |
| Flat poly bags | 1–4 mil (25–100 µm) | 2 mil is the everyday choice |
| Poly sheeting | 4–10 mil (100–250 µm) | 6 mil is the common general-purpose sheet |
How to choose poly bag thickness
When a new buyer is not sure, we ask four questions.
- What goes in the bag, and how heavy is it? Heavier contents need thicker film or a stronger resin. Thickness usually rises with bag size too: a 55-gallon liner at 0.5 mil will not hold up the way a small bag at 0.5 mil does.
- Does it have sharp edges or corners? Screws, broken glass and boxed items punch through thin film. Go thicker, or switch from HDPE to LLDPE.
- Single use or reusable? A single-use produce bag can be under 0.5 mil. A bag meant to be reused or shipped through a parcel network needs 2 mil or more.
- Who sees it? Thicker film looks and feels more premium on a shelf. Sometimes the right answer is the thinnest bag that still feels good in a customer’s hand.
Every extra mil costs resin, so the cheapest bag that works is the one you want. Don’t pay for 4 mil when 2 mil passes your drop test.
What to send us when you order
- Thickness in one unit, and say which: “1.5 mil” or “38 µm”. If you only know gauge, tell us whether it is a US or UK figure.
- Resin: HDPE, LDPE, LLDPE or a blend. If you don’t know, send a sample bag and we will match it.
- Size: width x length (plus gusset) in inches or cm.
- What goes in it, and how it ships or is displayed.
- Printing, if any: colors, one or both sides.
We make almost everything to custom size, from thin HDPE produce bags on roll to heavy poly sheeting. For trash bags by gallon size, see our trash bag size chart. Our plants follow Japan’s JIS standard and ISO 9001.
FAQ
How thick is 1 mil?
One thousandth of an inch, or 25.4 microns (0.0254 mm). That is about the thickness of a light kitchen trash bag or a bread bag.
Is 2 mil thicker than 25 micron?
Yes, about twice as thick. 2 mil is 50.8 µm. 25 µm is just under 1 mil.
Is mil the same as millimeter?
No. A mil is 0.001 inch (0.0254 mm). A millimeter is about 39 times thicker. “Mil” in the bag trade always means thousandths of an inch.
How do I convert gauge to micron?
Divide gauge by 4 for a close figure. 200 gauge is about 50 µm, which is 2 mil. In the US, 100 gauge is exactly 1 mil.
Why are some trash bags sold in microns and others in mil?
High-density bags are thin, so the trade quotes them in microns to avoid tiny decimals. Low-density bags are thicker and quoted in mil. Don’t compare the two numbers directly: a 16 µm HDPE liner and a 0.9 mil LLDPE liner can be equal performers.
Not sure what thickness your bag needs? Send us the product, the bag size and a photo of how it is used, and we will suggest a resin and thickness, with free samples from stock. Send us your spec.