Heavy Duty Plastic Bags for Industrial Use: A Sizing Guide

Most split-bag problems in a warehouse are not a thickness problem. They are a sizing problem. A bag that is 20mm too narrow gets forced over the load, the film stretches at the corners before anything is even lifted, and the first knock puts a hole in it. Buy the right size and a 100µm bag will outlast a 150µm bag that was always fighting its contents.

This is a practical guide to choosing size and gauge together for industrial work: machined parts, hardware, building materials, frozen bulk food, freight consolidation. QIS stocks 34 sizes of heavy duty plastic bags in five thicknesses, from 75x100mm up to 915x710mm, so the range is wide enough that there is almost always an exact match rather than a compromise.

What actually makes a plastic bag heavy duty

There is no legal definition, which is why the term gets used loosely. In practice, for LDPE poly bags, heavy duty means 100µm and above. The QIS range runs 35µm, 50µm, 75µm, 100µm and 150µm. The first three are light and general duty. The last two are the industrial gauges.

The 100µm bags handle sustained handling, cold storage, sharp edges and freight. The 150µm bags are the extra heavy duty option, available in a single size (455 x 700mm), for heavy machinery parts, building materials and anything where a puncture is expensive. Between them they cover most trade and warehouse work.

Worth knowing: all of these are virgin food grade LDPE, not recycled remill. That matters for food processors, but it also matters industrially, because virgin resin gives you consistent film strength batch to batch instead of the variable performance you get from reprocessed material.

Matching size to the load

How poly bag sizes are written

QIS product titles quote width first, then length. A bag listed as 205x305mm is 205mm across the opening and 305mm deep. Get this the wrong way around and you will order something that is the right area but the wrong shape, which is one of the most common ordering mistakes we see.

The measurement to take off your product is the widest point, not the average. For a boxed item, measure the widest face and add clearance. For an irregular part, measure the widest dimension in any orientation, because that is the dimension that has to pass through the opening.

Two rules that save returns:

• Add 10 to 20mm to the width. The bag has to slide on without stretching. A bag exactly the width of the product will be under tension before you have even sealed it.
• Add 40 to 60mm to the length if you are heat sealing. You need clear film above the contents to make the seal, and a seal made too close to the product is a weak seal.

The three size bands

Small, roughly 100 to 230mm wide. Fasteners, fittings, electrical components, small machined parts, spare parts kitting. These come in cartons of 1,000 or 2,000, because the jobs that use them use a lot of them.

Medium, roughly 230 to 330mm wide. The workhorse band. Hardware, tooling, component protection on the line, bulk food repacking, butcher and freezer portions. Carton quantities are typically 1,000 in the smaller sizes and 100 in the larger ones.

Large and extra large, 350mm wide and up. Building materials, freight consolidation, machinery parts, long items, bulk frozen goods. Sizes run out to 915mm, and these come in packs of 100 because of their bulk.

Three configurations that cover the majority of industrial orders:

Gauge and size work together

Film strength is not a fixed property of the bag. It depends on how much load the film is carrying per unit of area, which is a function of both thickness and how well the bag fits.

A generously sized 75µm bag with slack in it will often outperform a tight 100µm bag, because the slack lets the film deform around a corner instead of resisting it. LDPE fails by tearing from a stress point, and a tight fit builds those stress points in before you load anything.

So the sequence is: size first, gauge second. Get the dimensions right, then step the micron up if the contents are sharp, heavy, frozen, or going to be handled repeatedly. If you want the detail on gauge selection specifically, our poly bag thickness guide works through all five options, and the LDPE vs HDPE comparison covers why LDPE is the right base material for this kind of work.

Where a stock size genuinely does not fit, layflat LDPE tubing is the alternative. You cut it to the length you need and seal both ends, which suits long or awkward items such as extrusions, lengths of timber trim, or rolled goods that no flat bag will take.

Common industrial jobs and what to use

Sharp and abrasive parts. Screws, brackets, castings, cut metal. Go 100µm and size generously. The failure mode here is a corner working through the film during transit, and slack film resists that better than tight film.

Frozen and cold storage. LDPE stays flexible at low temperature rather than going brittle, which is the main reason it is the standard for freezer work. Use 100µm for anything held long term, and allow extra length so you can get a clean heat seal.

Freight consolidation. Large sizes, 100µm, used to keep a group of items together and dry inside a pallet or carton. This is where the extra heavy duty 150µm bag in 455 x 700mm earns its place, on loads with hard edges and real weight.

Dust and moisture barrier in storage. Electronics, documents, machined surfaces awaiting assembly. Gauge matters less here than fit and a proper seal. 75µm is usually sufficient.

Bulk food handling. Virgin food grade LDPE is safe for direct contact with fresh, dry and frozen food. For longer preservation, vacuum sealer bags do a different job, and for confectionery and pouch styles the plastic food bags range is a better fit than a flat poly bag.

Sealing and handling

Every poly bag in the range is open ended and heat sealable. For industrial use a heat seal beats a tie or a knot every time: it is tamper evident, it keeps moisture out properly, and it does not work loose in transit.

If you are sealing at any volume, a bench top unit from the heat sealers range pays for itself quickly. Keep spare elements and Teflon strips on hand, because the element is a consumable and a sealer with a worn element makes seals that look fine and fail later. There is a step by step walkthrough in our guide on using a heat sealer and replacing the element.

One handling note: do not lift a filled heavy duty bag by the top film alone. LDPE is strong in tension across the face but the top edge is a natural stress line. Support the base.

Buying in bulk

Poly bags are sold in bulk cartons, from 2,000 bags in the smallest sizes down to 100 in the largest heavy duty sizes, with tiered pricing that improves as volume rises. Prices move with resin and freight costs, so we do not publish them here. Live pricing is on each product page.

If you need volumes beyond the standard breaks, an ongoing supply arrangement, or a custom manufactured size that is not in the stock range, send the specs through the request a quote form or call 1800 555 343. Custom size runs are possible. QIS also backs orders with a 5% price beat guarantee, so bring a competing written quote if you have one.

Frequently asked questions

What micron counts as a heavy duty plastic bag?

For LDPE poly bags, 100µm and above. QIS stocks 100µm across a wide range of sizes and 150µm in a single extra heavy duty size (455 x 700mm). Below that, 75µm is a heavy general purpose gauge and 35µm to 50µm are light duty.

How do I work out what size bag I need?

Measure the widest point of the product and add 10 to 20mm to the bag width. Add 40 to 60mm to the length if you intend to heat seal, so there is clear film above the contents. QIS titles quote width first, then length, so 205x305mm is 205mm wide and 305mm deep.

Are heavy duty poly bags freezer safe?

Yes. LDPE stays flexible at low temperatures instead of turning brittle, which is why it is the standard material for freezer storage of meat, fish and prepared food. Use 100µm for long term frozen storage and heat seal rather than tie.

Can heavy duty plastic bags be used for food?

Yes. Every poly bag in this range is made from virgin food grade LDPE, not recycled remill, and is safe for direct contact with fresh, dry and frozen food. The distinction matters because food packaging must be made from certified food grade material with no contamination from previous use.

What if no stock size fits my product?

Two options. Layflat LDPE tubing lets you cut to length and seal both ends, which suits long or awkward items. For volume orders, custom manufactured sizes can be arranged. Call 1800 555 343 or use the quote form with your dimensions and quantity.

How fast do orders ship?

In stock poly bags ordered before 12pm on a weekday are dispatched same day from the Brisbane warehouse, with delivery across Australia including Sydney, Melbourne, Brisbane, Perth, Adelaide and regional areas. Freight timing to regional addresses varies. More detail is on our help and FAQ page.