3 Mil, 5 Mil, 10 Mil: Choosing Pouch Thickness

Laminating pouches are sold by thickness in mil — thousandths of an inch — and the figure quoted is per side. A 5 mil pouch is 5 mil of film on the front and 5 mil on the back, so the finished item gains about 10 mil overall plus the document.

This catches people out when they compare a pouch to a machine’s maximum rating, which is usually also quoted per side.

What each thickness is for

1.5 to 3 mil — flexible

Thin and bendable. The laminated sheet still behaves like paper: it can be rolled and it will crease if folded hard.

Right for menus that get replaced often, instruction sheets, price lists, anything filed in a binder. Also the cheapest per pouch and the fastest to run, because thin film reaches temperature quickly.

5 mil — the general-purpose choice

Semi-rigid. Holds its own shape when held at one edge but is not board-stiff. This is the thickness most offices standardise on.

Right for identity cards, notices, frequently handled reference sheets, and anything that will live on a wall or in a pocket for a year or more.

7 to 10 mil — rigid

Stiff enough to stand up on its own. Effectively a plastic card.

Right for luggage tags, badges, outdoor signage, teaching resources handled by children, and anything that needs to survive being dropped and stood on. Slow to run, and this is where machine compatibility becomes a real constraint.

Check the machine, not just the pouch

A laminator has a maximum pouch thickness. Feeding thicker film than the rollers are rated for produces one of two results: the film does not reach full temperature and the seal is cloudy and peels, or the pouch stalls between the rollers.

Most home and small-office machines top out at 5 mil. Machines rated to 10 mil generally have more heating elements and a slower drive.

If a machine has a thickness selector, use it — the setting changes the roller speed so the film has time to reach temperature.

Pouch size and the border

Buy pouches slightly larger than the document. A letter-size document in a letter-size pouch leaves almost no sealed border, and the seal is what keeps moisture out. A 3 mm to 5 mm border all round is what you want.

Never trim a pouch before laminating to make it fit. Cutting the sealed edge open means the adhesive squeezes out onto the rollers, which is the single most common cause of a ruined machine.

Trimming afterwards

Trim after laminating, and leave at least 2 mm of sealed border. Cutting flush to the document breaks the seal and the laminate will lift at the corner within weeks.

Rounding the corners is not decorative — square corners are where lifting starts and they are sharp on a card carried in a pocket. This is why so many kits include a corner rounder.

Matt or gloss

Gloss is more common, cheaper, and gives better colour saturation. Matt reduces glare, which matters for anything read under overhead lighting or photographed. Matt shows fingerprints less; gloss wipes cleaner.

Storing pouches

Flat, dry, out of direct sun. Pouches that have curled will feed crooked, and pouches stored somewhere warm can partially activate and stick together.

Working out what to buy

If you are stocking a single thickness for an office, 5 mil letter-size covers the majority of jobs. Add 3 mil if you laminate long documents that need to bend, and 10 mil only if you have a machine rated for it.

Our Laminating Pouches listings give the thickness and sheet size, and every machine in Thermal Laminators states the maximum thickness it accepts.