Gauge, mil and micron

Three units, one thickness

A mil is a thousandth of an inch. Gauge counts hundredths of a mil, which is how US film is sold. Micron, a thousandth of a millimetre, is how most of the rest of the world writes it, and it appears on imported film and on many data sheets.

To go the other way, micron to gauge, divide by 25.4 and multiply by 100: a 23 micron film is about 90 gauge. The micron column is rounded; it's close enough to compare rolls, not to specify a film to a mill.

True gauge and equivalent gauge

True gauge is the thickness of the film on the roll. Equivalent gauge is the thickness of ordinary film that a different product is meant to replace. You meet it on pre-stretched hand film and on some high-performance films made from stronger resins, which are physically thinner than the gauge they are sold against.

A buying guide's advice is to compare pre-stretched film on its equivalent gauge.² The reason is in the numbers: one wrapper maker says 65 gauge film pre-stretched 250 percent ends up about 26 gauge on the load.¹ Thickness on the roll and thickness on the pallet are different things; equivalent gauge tries to talk about the second.

When the units trip people up

• A quote in micron next to a quote in gauge: convert one before comparing price per roll.
• "Mil" and "micron" both start with an m; 1 mil is about 25 times thicker than 1 micron.
• An equivalent-gauge roll next to a true-gauge roll: compare loads wrapped per roll, not thickness.

Widths in millimetres

Imported rolls are often labelled in millimetres for width and metres for length as well as micron for thickness. The same arithmetic works: divide millimetres by 25.4 for inches, so a 500 mm roll is about 19.7 inches, close to the common 20 inch machine width, and a 450 mm roll about 17.7 inches, just under the 18 inch hand roll. For length, a metre is about 3.28 feet, so 1,500 metres is roughly 4,920 feet. Check the core too: metric rolls are not always on the 3 inch cores US dispensers and carriages expect.

Checking a roll yourself

You cannot read thickness by eye, and a pocket micrometer on a single layer of soft, clingy film gives a loose answer at best. The honest check is the label and the supplier's data sheet. What you can measure is what matters at the dock: feet per roll, against what the label says, by weighing a full and an empty core; loads wrapped per roll; and containment force on finished pallets. Those three tell you whether a cheaper roll is actually cheaper.

What the rest of a data sheet says

A maker's sheet lists more than gauge: tensile strength, how far the film stretches before it breaks, puncture and tear resistance, and cling. Treat these as a way to compare two films from the same sheet layout, not as promises about your pallets. Ask for the sheet with the quote, and test on your own loads before committing to a monthly quantity.

Once you have the gauge, the gauge chart matches it to a load weight, and pre-stretched hand film shows the equivalent-gauge idea in a product.

Why the US kept gauge

Gauge as a measure of plastic film thickness is a trade convention, convenient because it turns small decimals into whole numbers: buyers say "eighty" rather than "point eight mil". Most other countries use micron. Neither unit says anything about strength or stretch by itself; two films at the same gauge can behave very differently depending on resin, layers and how they were made.

Thickness tolerance

No film is perfectly even. Cast film's thickness varies less across the web than blown film's, which is one reason cast stretches more predictably on a carriage. Data sheets sometimes state a tolerance, a range around the nominal gauge.

Gauge in other materials

The word gauge also measures sheet metal and wire, where bigger numbers mean thinner material. Film gauge runs the other way: bigger numbers mean thicker film.

Rounding

Round micron conversions to whole numbers; nobody stocks 66.9 gauge.

Questions readers ask

Is a 12 micron film really as strong as 80 gauge?

Not by thickness: 12 micron is under half a mil. High-performance films made from stronger resins can hold what a thicker ordinary film holds, which is the idea behind equivalent gauge. Whether one does on your pallets is a matter of testing containment force, not of the label.

Our European parent company specifies film in micron. How do we buy it here?

Convert micron to gauge, as above, and round to the nearest gauge US suppliers stock. A 17 micron specification, for example, is about 67 gauge, so 63 or 70 gauge is the nearest common choice. Confirm the switch with containment tests at your site.

Why are some cases marked in mil instead of gauge?

Heavier films and some imported or industrial products are labelled in mil. A 1.5 mil film is 150 gauge. The arithmetic is the same either way.

Does gauge tell me the weight of a roll?

Only together with width and length. Two rolls of the same gauge and width weigh the same per foot, so the heavier roll has more feet on it, or a heavier core.

Are gauge numbers the same in Canada?

Canadian buyers use both gauge and micron, so check which a quote uses; Mexican suppliers mostly quote micron.

Facts on this page last reviewed 2026-11-13.