Two poly bags can look identical on the shelf and behave completely differently in the hand. One holds a kilo of snapper through a week in the freezer; the other splits the moment you drop a handful of bolts into it. The difference is almost always thickness — measured in microns (µm), and it's the single spec most people get wrong when they order.
Order too thin and you're double-bagging, cleaning up spills and fielding complaints. Order too thick and you're paying for strength the job never uses. This guide walks through what a micron actually is, what each thickness in the QIS range is built for, and how to match the gauge to your product so every bag does its job the first time.
What a micron (µm) actually means
A micron — written µm — is one-thousandth of a millimetre. When a poly bag is described as 35µm, that number is the thickness of the plastic film itself, not the size of the bag. A 50µm bag is around 40% thicker than a 35µm bag of the same dimensions, so it resists tearing and puncturing under heavier or sharper loads.
In Australia, poly bags are almost always specified in microns. You'll occasionally see "gauge" quoted on imported or older product listings — that's a US and UK convention, and it measures the same thing a different way (100 gauge is roughly 25µm). Stick to microns and you're comparing like for like across the whole poly bag range.
Thickness drives three things that matter on the packing bench: strength (heavier film resists tears and punctures), cold-weather flexibility (heavier LDPE stays supple in the freezer instead of going brittle), and cost per bag (thinner film is cheaper, which adds up fast at high volume). The trick is buying exactly enough gauge for the job — no more, no less.
The five poly bag thicknesses, and what each is for
QIS stocks LDPE poly bags in five thicknesses, from 35µm right up to 150µm. Here's the quick version before we go into detail:
| Thickness | Grade | Built for |
|---|---|---|
| 35µm | Standard | Fresh produce, bakery, small retail, dry ingredients, general food packing |
| 50µm | Medium | Butcher-counter portioning, larger bakery items, moderate-weight retail, garments, spare parts |
| 75µm | Heavy | Bulk food, freezer storage of meat and fish, warehouse components, semi-industrial |
| 100µm | Heavy duty | Frozen goods, sharp or heavy items, freight, industrial packaging |
| 150µm | Extra heavy duty | Heavy machinery parts, building materials, extra-heavy freight |
35µm — Standard
The everyday workhorse, and the most popular thickness in the range. If you're bagging fruit and veg at a greengrocer, sliding bread rolls or biscuits across a bakery counter, or packing small dry-goods retail lines, this is almost certainly your bag. It's light-duty by design, which keeps the cost per bag down when you're getting through cartons of two thousand at a time. For high-volume, low-weight jobs, going heavier just adds cost with no real benefit.
50µm — Medium
A step up in puncture resistance for slightly heavier or more awkward contents. This is the gauge butchers reach for when portioning cuts at the counter, and it suits larger bakery items, moderate-weight retail goods, garment packaging and spare parts. If your 35µm bags are occasionally nicking or stretching at the seams, 50µm is usually the fix.
75µm — Heavy
A genuine durability jump for heavier products and colder storage. Think butcher wholesale portions, freezer storage of meat and fish, bulk food repackaging and warehouse component packing. At 75µm the film shrugs off the sharp corners and sustained weight that would work a lighter bag loose.
100µm — Heavy duty
Built for frozen goods, sharp or heavy items, freight and industrial packaging. This is the gauge for long-term frozen storage, seafood processing, machinery parts and hardware with edges that would slice through a thinner bag. It handles repeated handling and cold storage without turning brittle.
150µm — Extra heavy duty
The toughest film in the range, for the toughest jobs — heavy machinery parts, building materials and extra-heavy freight where puncture resistance is non-negotiable. It's a specialist line, currently stocked in a single 455 × 700mm size.
How to choose the right thickness for your job
The fastest way to land on the right gauge is to work back from the contents. Ask yourself three questions: how heavy is it, does it have sharp edges or corners, and where does it end up — a shelf, a freezer or a freight pallet?
Produce, bakery and light retail. Smooth, light contents that move quickly. 35µm does the job and keeps your cost per bag as low as it goes.
Butchers, delis and general food service. Moist and slightly heavier contents, often portioned by hand all day. 50µm gives you the extra puncture resistance without over-spending; step to 75µm for wholesale portions or anything bound for the freezer.
Freezer and cold storage. Cold makes cheap plastic brittle. LDPE stays flexible at low temperatures, but you still want gauge behind it for long stints — 75µm to 100µm for meat, fish and prepared meals held for weeks. (If you're weighing up which bags survive the freezer at all, our freezer bag guide breaks it down.)
Warehouse, industrial and freight. Weight, edges and rough handling. 100µm covers most sharp or heavy items and freight consolidation; 150µm is there for building materials and machinery parts that would defeat anything lighter.
eCommerce fulfilment. A poly bag inside the carton keeps product clean and dry in transit. 35µm to 50µm suits most soft goods; go heavier if the item is sharp or heavy enough to threaten the outer parcel.
A reliable rule of thumb: buying a heavier gauge than the job needs adds cost with no benefit, while going too light means split bags and double-bagging. When you're genuinely between two thicknesses, size up — the few extra cents per bag are cheaper than a ruined product and a re-pack.
Same size, three gauges — see the difference
Because thickness is independent of dimensions, you can order the exact same footprint in different microns and match it to different jobs. Here's one popular 205 × 305mm size across three gauges — the same bag, built for standard, medium and heavy-duty work.
Thickness isn't the only spec to get right
Micron is the headline number, but a few other details decide whether a bag actually suits your operation.
Size. Poly bags are measured length × width, and the range runs from 75 × 100mm up to 915 × 710mm across 34 sizes. Match the bag to the product with a little room to seal — too tight and you can't close it cleanly; too loose and you're wasting film. You can filter the poly bag collection by width, length and thickness to find your exact combination.
Food-grade LDPE. Every poly bag in this range is made from virgin food-grade LDPE, not recycled remill. That matters for anything touching food — bread, produce, meat, fish, dairy and prepared meals — because food packaging needs to be made from certified food-grade material with no carry-over from a previous use. If you want the full material comparison, our paper versus plastic bag guide covers where each one earns its place.
Sealing. These bags are open-ended for fast filling and heat-sealable for a tamper-evident finish that beats a knot or a tie. A bench-top or hand-held unit from the heat sealers range turns a stack of open bags into sealed, retail-ready packs.
Reusable or resealable? If your customer needs to open and reclose the bag — storing components, portioning, kitchen prep — a press-seal bag is the better tool than a heat-sealed poly bag. The resealable press-seal range covers that. For long-term food preservation, vacuum sealer bags pull the air out entirely, and for cut-to-length custom sizing there's layflat LDPE tubing.
Buying poly bags in bulk
Poly bags are priced for high-volume daily use, so they're sold in bulk cartons — from 2,000 bags for the smaller sizes down to 100 for the largest heavy-duty gauges. Larger orders drop the per-bag price through volume tiers, which is where a busy kitchen, warehouse or fulfilment operation makes real savings.
If you need a size that isn't in stock, a custom-printed bag with your logo, or an ongoing supply arrangement, the QIS team can arrange custom manufacturing runs — request a bulk quote or call 1800 555 343. Orders placed before 12pm on weekdays dispatch same day from the Brisbane warehouse, Australia-wide, and every line is backed by the 5% price-beat guarantee.
Poly bag thickness FAQ
What thickness poly bag do I need?
Match it to the contents. 35µm for light produce, bakery and small retail; 50µm for butchers, deli and heavier retail; 75µm for bulk food and freezer storage; 100µm for frozen, sharp or heavy items and freight; 150µm for the heaviest industrial and building jobs. When you're between two, size up.
Is a thicker poly bag always better?
No. Thicker film costs more per bag and, past a point, adds strength the job never uses. For high-volume light-duty work like bagging produce, a 35µm bag performs as well as a 100µm one and costs a fraction as much. The goal is the right gauge, not the heaviest.
What's the difference between microns and gauge?
They measure the same thing — film thickness — in different units. Microns (µm) are the Australian standard; gauge is a US and UK convention you'll sometimes see on imported listings. As a rough conversion, 100 gauge is about 25µm. Comparing everything in microns avoids mix-ups.
Are thicker poly bags safe for food and freezing?
Every poly bag in the QIS range is virgin food-grade LDPE and safe for direct food contact at any thickness. LDPE also stays flexible in the cold instead of going brittle, so it freezes well — heavier gauges (75µm–100µm) simply hold up better over long freezer stints. Our freezer bag guide has the detail.
What's the most popular poly bag thickness?
35µm. It's the standard everyday gauge across produce, bakery, food service and general retail, and it's stocked in the widest spread of sizes because it covers the most jobs at the lowest cost per bag.
Can I get poly bags thicker than 150µm, or in a custom size?
150µm is the heaviest stocked gauge, in a single 455 × 700mm size. For heavier film, non-stock sizes or custom-printed bags, QIS can arrange a manufacturing run to spec — request a quote or call 1800 555 343.
Not sure which micron to order?
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