What does micron mean in plastic bags?

One micron is one thousandth of a millimetre, and it is the thickness of the film wall. A 50 micron bag has walls of 0.05 mm. It is the number that decides how strong the bag is and how much it costs, because LDPE is sold by weight and thickness drives weight directly.

How do I convert micron to gauge?

Multiply micron by 4. So 50 micron is 200 gauge, 100 micron is 400 gauge, and 200 micron is 800 gauge. Indian suppliers use both units freely, sometimes in the same sentence, so it is worth being able to convert in your head.

What is GSM in plastic film?

Grams per square metre. For LDPE, GSM is roughly micron multiplied by 0.92, because that is the density. So 100 micron film weighs about 92 GSM. It is a useful unit when you are comparing plastic against paper or non-woven alternatives, which are always quoted in GSM.

How can I check if my bags are the right thickness?

Weigh ten bags and divide by ten, then compare with the formula: 2 x width in cm x length in cm x micron x 0.92, divided by 10,000, gives grams per bag. Within 5 percent is normal. Consistently 10 percent light means the film is thinner than you ordered, whatever the invoice says.

Is a thicker bag always better?

No, it is just more expensive. Thickness multiplies your material cost on every order forever, so it should be paid for a real failure mode: hard corners, base-seam load, sun exposure or abrasion. Most specs we review are one step thicker than the job needs, usually because nobody has revisited them in years.

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Micron, gauge and GSM: the buyer's guide

Micron is the single most important number on an LDPE quote, and the easiest one to quietly change. This page explains what it means, how it converts, which thickness suits which job, and how to verify what arrived on your dock.

Ask which micron you need →

CONVERSIONS YOU WILL ACTUALLY USE

1 micron = 0.001 mm. So 100 micron is a tenth of a millimetre.
Micron to gauge: multiply by 4. 50 micron = 200 gauge. 200 micron = 800 gauge. Indian trade uses both, often in the same conversation.
Micron to GSM for LDPE: multiply by 0.92. 100 micron film is about 92 grams per square metre.
Micron to mil (US): divide by 25.4. 100 micron is about 3.9 mil.
Weight of film: area (m²) x micron x 0.92 / 1000 = kilograms.

A thickness for every job

Everything we make, with the range it usually lands in and the reason.

Product	Micron	Driven by
Garment and retail bags	25 to 50	Cost. Nothing heavy, no corners, single use.
General poly bags	30 to 80	Product weight. Under 1 kg go 30 to 50, above go 60 to 80.
Courier mailers	50 to 80	Handling abuse in sorting, plus tamper resistance.
Food and bread bags	25 to 60	Clarity and cost, with 30 to 40 the bakery standard.
Pouches and FFS film	40 to 120	Seal reliability on the machine, not strength.
Drum and container liners	75 to 150	Puncture resistance at the drum rim.
Curing sheet	100 to 150	Foot traffic on site.
DPC and vapour barrier	200	It is buried for the life of the building.
Machine and pallet covers	60 to 200	Indoor versus outdoor, and wind flap.
Grow bags	200 to 400	Wet soil load on the base seam, plus root pressure.
Mulch film	25 to 50	One season versus two, plus laying handling.

How to check the gauge of what you received

Do this on the first delivery from any new supplier. It takes ten minutes and it is the only real defence against a quiet gauge cut.

Method 1: the scale (no instruments needed)

Weigh ten bags together on a kitchen scale, then divide by ten to get grams per bag.
Calculate what the bag should weigh: 2 x width (cm) x length (cm) x micron x 0.92 / 10,000 = grams.
Compare. Within about 5 percent is normal commercial variation. Ten percent or more under, consistently, means the film is thinner than specified.

Example: a 16 x 24 inch bag at 60 micron should weigh about 27 grams. If your ten bags average 23 grams, you are being supplied something closer to 50 micron.

Method 2: the micrometer

Measure at five or six points across the bag and average them. Two things trip people up: a folded bag reads double thickness, so halve it, and a single spot reading tells you nothing because film has natural variation across the web. Average or do not bother.

Method 3: roll weight for film

For a roll, net weight divided by (width in metres x length in metres x 0.92) gives you the average micron. This is the cleanest check available, because it averages across the whole roll rather than sampling.

Send us a sample and we will measure it for you

Courier a few bags or two metres off a roll. We will report the actual gauge, the blend and whether you are over-specced, at no cost and with no obligation to order.

Send a sample

Why "just go thicker" is bad advice

Thickness is a direct multiplier on cost, because LDPE is sold by weight. Going from 60 to 80 micron adds 33 percent to your material bill on every order, forever. That is worth paying when the failure mode is real, and pure waste when it is not.

The failure modes that genuinely need more micron: puncture from hard corners, load on a base seam, sun exposure, and abrasion in transit. The failure modes that do not: a customer who once complained, or a spec nobody has revisited since 2019.

What we do on a comparison quote is check whether the incumbent spec is doing real work. Over-specced bags are the single most common thing we find, and correcting it is a permanent saving rather than a one-off discount. Details on the price guide.

Keep reading

Price guide

How micron feeds into price, and how to compare quotes honestly.

Quality and specs

The tolerances we hold on thickness and variation.

LDPE vs LLDPE

How a blend can let you drop a micron step without losing performance.

Thickness questions

Let us pick the micron

Describe what goes in the bag, its weight and how it gets handled. We will name one micron and explain the reasoning, then quote it. Free either way.