What Is Fleece Fabric? What It's Made Of, Warmth and Pilling

What is fleece fabric, exactly? In most stores it's polyester, a knit made from plastic based fiber that has been brushed until the surface turns into a soft, lofty pile that traps warm air. Every October it comes back out of the closet as zip jackets, quarter zips, throw blankets and the fuzzy inside of half the sweatshirts on the rack.

The name borrows from a sheep's coat, but modern fleece rarely contains any wool at all. Knowing what's actually on the label explains why one fleece stays soft for a decade while another is covered in pills before winter is over, and why two jackets that look identical can grade very differently.

What Is Fleece Fabric Made Of?

The fleece most people picture is polyester fleece, often sold as polar fleece. It was developed in the late 1970s by Malden Mills, a Massachusetts textile mill, as a lighter, quicker drying alternative to wool for outdoor clothing. The process is easy to describe. Polyester yarn is knitted into fabric, run past rollers covered in fine wire that pull fibers up from the surface, then sheared so the pile sits at an even height. That brushed surface is what makes fleece feel soft and look fuzzy.

A growing share of that polyester is recycled, usually from plastic bottles. Chemically it's the same fiber, so it feels, insulates and wears like virgin polyester. If you want the fiber basics, our guide to polyester fabric covers them in detail.

The second big category is cotton fleece, the fabric inside most sweatshirts and sweatpants. It's knit with small loops on the back, and those loops are brushed into a soft nap. Leave the loops unbrushed and you get French terry instead. Cotton fleece is often blended with polyester, anywhere from a small percentage up to a 50/50 split, to limit shrinkage and help it hold its shape.

You'll also find nylon fleece in some activewear and a little wool fleece in technical base layers. In other words, "fleece" describes how a fabric is built and finished, not what fiber it contains. The composition label is the only place that tells you.

Polar Fleece vs Microfleece and Other Types

Polar fleece is the classic thick version, usually brushed on both sides for maximum loft. Outdoor brands often sell it by weight. A 100 weight fleece is light enough for layering, 200 weight is the all purpose midweight, and 300 weight is the heavy option you can wear as a jacket on a dry, cold day.

Microfleece is knit from much finer polyester filaments, so it's thinner, lighter, smoother and less bulky. It packs small and slides easily under a shell or a sweater, but it isn't as warm as a thick polar fleece. If you want one fleece that works from September through March, a midweight polar fleece is usually the better buy. If it will live under a winter coat, microfleece makes more sense.

Then there are the variations. Anti pill fleece has been finished to reduce loose fiber ends on the surface, which matters more than almost anything else on the hang tag. Grid fleece has a waffle pattern of channels on the inside to move air during exercise. Sherpa, the curly faux sheepskin pile inside many denim jackets, is a close cousin of fleece with a different texture and a different set of problems.

Is Fleece Warm?

Yes, and for its weight it's one of the warmest fabrics you can buy. Warmth in clothing comes mostly from trapped air, and fleece's brushed pile holds a lot of air with very little fiber. Ounce for ounce, a midweight fleece can feel as warm as a noticeably heavier knit sweater.

Polyester also absorbs almost no water. That means fleece dries quickly and keeps most of its insulation when it gets damp from drizzle or sweat, which is a big reason it replaced cotton sweatshirts for hiking and camping decades ago. A wet cotton sweatshirt pulls heat away from your body. A damp fleece mostly doesn't.

The weakness is wind. Fleece is a loose, open structure, so a cold breeze passes straight through it. On a still November afternoon a fleece alone is plenty. On a windy one, it works best as a midlayer under a jacket that blocks the wind.

Breathability, Static and Odor

Fleece is a bit of a paradox on breathability. Air moves through it easily, which is why it feels comfortable on a brisk walk. But polyester fiber doesn't absorb moisture the way cotton or wool does. Sweat either escapes as vapor or sits on the fiber surface, and against bare skin that can feel clammy once you warm up.

That's why WearScore rates polyester's breathability as poor even though fleece jackets feel airy. The rating reflects how the fiber handles moisture against your body, not just whether wind can get through the knit.

Two other quirks show up in winter. Polyester builds static in dry indoor air, so fleece crackles, clings and collects lint and pet hair. It also tends to hold onto body odor more than natural fibers do, so a fleece worn for a few hard days needs a real wash rather than an airing out.

Fleece vs Wool

This is the comparison most cold weather shoppers are really making, and neither fiber wins outright. Here's how they stack up for typical fall and winter use.

Wool wins on comfort over a long day, odor control and longevity when it's cared for properly. Fleece wins on price, weight, drying speed and easy washing. For sitting around a fire pit or wearing all day at the office, wool feels better. For a rainy hike or a kid who will drag the jacket through the mud, fleece is the practical choice. Our wool guide explains why the grade of wool matters so much on the other side of this comparison.

Why Fleece Pills, and What Anti Pill Actually Means

Pilling is fleece's biggest long term problem, and it's built into how the fabric is made. Brushing deliberately loosens fiber ends on the surface. Friction from backpack straps, seat belts and your own arms swinging twists those loose ends into little balls. Because polyester is so strong, the balls don't break off the way weaker cotton or wool pills do. They stay anchored and keep collecting more fiber.

Anti pill fleece is sheared and finished to remove and stabilize those loose surface fibers, so it resists pilling far better than cheap untreated fleece. It isn't pill proof, but it's the most useful thing to look for on a fleece hang tag. Denser, tightly knit fleece also tends to outlast thin, loose, extra fluffy fleece. Our guide on how to stop clothes from pilling covers how to remove pills without damaging the pile.

The fiber matters too. In WearScore's index of 33 garments sold as fleece, most are cotton rich sweatshirt fleece rather than polyester. The four that earned a B were 87 to 91% cotton, while the four that graded F were all polyester dominant, including two 100% polyester full zip jackets. The app rates polyester as a high pilling risk, so a pure polyester fleece starts at a disadvantage no matter how soft it feels in the store.

Microfiber Shedding and How to Wash Fleece

Brushed synthetics like fleece are among the fabrics most associated with microfiber shedding. Each wash can release tiny polyester fibers that are small enough to slip through wastewater treatment, and recycled polyester sheds just like virgin polyester. We dig into that in our piece on recycled polyester and microplastics.

The good news is that gentle care reduces shedding and keeps fleece looking new longer, so the same habits do double duty:

• Wash fleece less often. Airing it out between wears is usually enough.
• Use cold water, a gentle cycle and a full load to cut down on friction.
• Turn it inside out and close the zippers so they don't snag the pile.
• Skip fabric softener, which coats the fibers and flattens the loft.
• Air dry or tumble on low. High heat can melt and mat the surface.
• Consider a wash bag or washer filter designed to catch microfibers.

Never iron fleece, and keep it away from campfire sparks, which can melt small holes straight through it.

The Honest Answer on Fleece

Fleece earns its place in a fall and winter wardrobe. It's warm for its weight, dries fast, washes easily and costs a fraction of what wool does. For outdoor layers, blankets and kids' jackets, it's hard to beat.

Where it falls short is anywhere comfort against skin and longevity matter most. Pure polyester fleece pills, holds odor, builds static and sheds microfibers, and those weaknesses add up over years of wear. Cotton rich sweatshirt fleece breathes better and ages more gracefully, and wool still wins for all day comfort.

The practical move is to check which kind of fleece you're actually buying. Scan the label with WearScore and you'll see the real fiber mix behind the word fleece, along with the pilling risk, care complexity and whether it's dryer safe, so you know which fleece will still look good next October.