If you have ever shopped for plastic bags, poly bags or plastic film, you have probably seen a thickness listed as something like 50µm or 200µm and wondered what it actually means. Here is a plain-English explanation, and why it matters when you are choosing the right packaging.
What does µm mean?
µm is the abbreviation for a micrometre, more commonly called a micron. One micron is one-millionth of a metre, or one-thousandth of a millimetre, so it is a very small unit used to measure very thin things.
You will sometimes see it written as um or micron. They all refer to the same measurement. The µ symbol means micro and comes from the Greek alphabet.
Why microns matter in packaging
In the packaging industry, microns measure the thickness of plastic, from thin produce bags right through to heavy-duty industrial liners. As a general rule, the higher the micron number, the thicker, stronger and more durable the plastic:
- Thin films (around 20 to 35µm) suit light retail and produce use.
- Medium films (50 to 75µm) are ideal for general storage and resealable bags.
- Heavy-duty films (100µm and above) are built for sharp, heavy or industrial products.
Manufacturers measure thickness with a tool called a micrometer, which reads how many microns thick a sample of plastic is.
Microns and Australian plastic bag laws
Micron thickness is not just about strength, it is also tied to legislation. Across many Australian states and territories, lightweight single-use plastic bags under 35µm are banned. Choosing compliant, reusable-thickness bags keeps your business on the right side of the rules.
How to choose the right thickness
The best micron rating depends on the weight and shape of what you are packing. Heavier or sharper items need a higher micron count to avoid tears, while lighter items can use a thinner, more economical film.
Shop plastics by thickness at QIS Packaging
- Plastic poly bags — food-grade LDPE from 35µm to 150µm
- Layflat tubing — 30µm to 150µm
- Resealable ziplock bags — including heavy-duty 75µm
- Builders film — 100µm and 200µm sheeting
Related guides
Want to understand the plastics themselves? Read What is LDPE?, What is HDPE? and the difference between LDPE and HDPE.
Not sure which thickness you need? Contact our Brisbane team and we will help you choose the right micron for the job.
