Trash Liner Mil vs Gauge vs Microns: Buy on Cost Per Pull, Not Cost Per Case
The short answer: mil and micron are just two units for the same thing — film thickness — and neither one tells you how strong a trash liner is any more. Low-density liners are labelled in mils, high-density liners in microns, and a high-density bag at a third of the thickness routinely carries the same load as a low-density one. The number that should drive a wholesale order is cost per pull at the load your cans actually see, and it takes a minute to compute from the spec sheet. Here are the units, the manufacturer tables, and the math.
Mil, micron, gauge: the same ruler in three languages
A mil is one thousandth of an inch (0.001″). A micron is one thousandth of a millimetre, and 25.4 microns equal one mil. “Gauge” is simply the trade word for whichever of those a manufacturer prints. Heritage Bag’s Can Liners 101 guide states the convention plainly: linear low-density (LLDPE) liners are measured in mils, and high-molecular-weight high-density (HMW-HDPE) liners in microns. Low-density liners run from about 0.35 to 4.0 mil; high-density liners from about 6 to 24 microns, which is only 0.24 to 0.94 mil. So a “16 micron” high-density can liner is thinner than a “0.65 mil” low-density one, and that is precisely why comparing the two numbers directly leads buyers to the wrong bag.
Why thickness stopped meaning strength
Two things happened. Resins improved — Inteplast’s Pitt Plastics guide notes HMW-HD film is roughly three times stronger than ordinary polyethylene of the same thickness, which is why it can be run at about a third of the gauge — and the industry moved to named strength tiers (Light, Medium, Heavy, Extra Heavy) instead of gauge. Heritage’s own guide puts it in five words: “Thickness doesn’t matter, strength matters.”
The standards bodies agree, in their own way. The two ASTM tests that describe how a liner fails in a can — D1709 (dart impact, the dropped-can-of-soup test) and D1922 (Elmendorf tear, the snag-on-a-rim test) — both state that results cannot be compared across different thicknesses. In other words, even the test methods refuse to let you rank bags by mil.
What to read instead: the load rating
Manufacturers publish a static-load figure for every liner. Heritage prints it as a tier with a weight range; Inteplast prints a Max Load column in pounds on each spec sheet. Heritage’s published bands are the quickest reference:
| Tier | HDPE (microns) | LLDPE (mil) | Static load |
|---|---|---|---|
| Light | 6–9 | 0.30–0.49 | 10–25 lb |
| Medium | 10–12 | 0.50–0.60 | 21–50 lb |
| Heavy | 13–14 | 0.61–0.74 | 31–60 lb |
| Extra Heavy | 15–17 | 0.75–0.80 | 41–70 lb |
| XX / XXX Heavy | 18–22 | 1.10–3.00 | 61–90 lb |
Ranges combine Heritage’s separate HDPE and LLDPE tables; the load column shows the span across both resins for each tier name. Use the exact SKU sheet for ordering.
The tiers explain the pattern buyers find confusing: a 13-micron high-density liner and a 0.70-mil low-density liner are both labelled “Heavy,” and Heritage rates the high-density one for the higher static load (51–60 lb against 31–40 lb) even though it is about half the thickness.
The cost-per-pull math
Cost per pull is the case price divided by liners per case, but only after you have matched the load rating to the can. Here is a real pairing from Inteplast’s published sheets, both 33-gallon, both rated Max Load 75 lb:
- High-density MR33403MC — 33×40, 16 micron, 250 liners per case, 14.0 lb of resin per case.
- Low-density B74040XK — 33×39, 1.30 mil, 125 liners per case, 14.0 lb of resin per case.
Same manufacturer, same load rating, the same 14 pounds of plastic in the box — and twice the pulls from the high-density case. Since a case price tracks resin weight closely, the high-density liner lands at roughly half the cost per pull for identical rated capacity. Run it with your own quote: at, say, $28 a case the HD bag is about 11 cents a pull; at $30 a case the LLDPE bag is 24 cents (example math — substitute your invoice). A 200-can office building pulling once a day is 6,000 pulls a month, so the choice is worth roughly $770 a month on that one SKU.
Now the trap that reverses it. Inteplast’s 0.65-mil version of that low-density bag (B74020XK) also comes 250 to a case, but is rated Max Load 50 lb. Put it on a 33-gallon can that regularly hits 60 pounds of wet kitchen waste and the bag fails, the porter double-bags, and the real cost per pull doubles while the invoice looks cheaper. Cost per pull only works when the load rating is right first.
Pick the resin by what goes in the can, then the tier by weight
Both manufacturers give the same rule. High-density for waste without sharp edges — office paper, restroom waste, most food service — where it delivers high dart-impact strength at low gauge; its weakness is tear propagation, so one puncture from a broken bottle runs. Linear low-density for sticks, glass, metal cans, construction debris and anything jagged, where its tear resistance matters more than its weight. Then use the load tier, not the gauge, to size the bag to the heaviest load that can actually sees. Our can liner sizing guide covers matching dimensions to the can, and the supplies calculator turns can count and pulls per day into cases per month.
Two things to check on the case before you accept it
First, the bottom seal. Heritage and Inteplast both describe the star seal as the one that maximizes carrying capacity and virtually eliminates leaks, because it has no gussets and no corners for liquid to sit in; gusseted seals are sealed through four layers and are described by both as an inherently weak bottom. For wet waste, specify star seal.
Second, the label. Under the NIST case-labelling requirement that Heritage reproduces in its guide, a case must state actual size, gauge, capacity, case pack and case weight, and the words “Equivalent To,” “EQ” and “Nominal” are not accepted as a product specification. A case marked “EQ 1.0 mil” is telling you the maker would rather you not know the real gauge. Weigh the case if in doubt: resin weight per case is the honest number, and it is printed on every legitimate spec sheet.
How to run the order
- List each can size and the heaviest load it sees in a week.
- Choose resin by contents: HD for smooth waste, LLDPE for sharp.
- Choose the load tier from the manufacturer sheet, not the gauge.
- Divide case price by liners per case for every candidate at that tier.
- Specify star seal for anything wet, and reject “EQ” or “nominal” labels.
Bring that list to our wholesale trash liners and bags range and we will quote it by the case, or send your current invoice and we will price it line by line at the same load ratings.
FAQ
Is a higher mil trash bag always stronger?
No. Mil only measures thickness, and manufacturers state that gauge is no longer a reliable indicator of strength. A 16-micron high-density liner (about 0.63 mil) can carry the same rated load as a 1.30-mil low-density liner. Compare the published load rating, not the gauge.
How do I convert microns to mil?
Divide microns by 25.4. A 12-micron liner is about 0.47 mil; a 22-micron liner is about 0.87 mil. Going the other way, multiply mil by 25.4.
What does cost per pull mean for trash liners?
Case price divided by liners per case, compared only between bags with the same load rating for the same can. It is the number that reflects what you actually spend, because a bag that fails and gets double-bagged costs two pulls.
When should I use low-density instead of high-density liners?
When the waste is sharp or jagged: glass, metal, sticks, construction debris. Low-density film resists tear propagation; high-density film has excellent puncture and impact strength but tears further once cut, so it belongs on smooth waste like paper, restroom and most food-service refuse.