What is cotton? Where it comes from and how it is made

Where cotton comes from

Cotton grows on the seed. Each fiber is a single cell that sprouts from the skin of a cotton seed inside the boll, and by the time the boll opens, that cell is more than 90% cellulose. Cotton was domesticated four separate times in different parts of the world. Today about 90% of the cotton grown commercially is one species, Upland cotton (Gossypium hirsutum). Most of the rest is Gossypium barbadense, the extra-long-staple cotton sold as Pima and Egyptian cotton.

China grows the most. In the 2025/26 season USDA counted 35.8 million bales from China, 23.8 million from India, 18.75 million from Brazil and 13.9 million from the United States.

How cotton is made into fabric

In the US the crop is picked by machine and packed into modules in the field. At the gin, the seed cotton is dried and cleaned, and spinning saws pull the fiber, called lint, through ribs that are too close together for the seeds to follow. The lint is pressed into bales of about 500 pounds, and each bale is graded for length, strength and color.

At the mill, bales are opened and blended, then carded into a loose web, which clears out trash and short fibers. Some cotton is also combed, which removes more of the short fibers and gives a smoother, stronger yarn. That’s what “combed cotton” means on a label. The fiber is then drawn out and spun into yarn.

Nothing in that process changes what the fiber is. A cotton shirt is made of the cells that grew on the seed.

Cotton and polyester

	Polyester	Cotton
What it is	Plastic (PET), mostly from fossil fuels	Seed fiber, over 90% cellulose
Share of world fiber, 2024	59%	19%
EU conventional moisture value	1.5%	8.5%
Odor after a workout	More intense, less pleasant	Less intense
Yarn in lake water	Did not appreciably degrade	More than 70% biodegraded

Is cotton breathable?

Cotton takes up water. The moisture value EU rules assign to cotton is 8.5%, more than five times polyester’s 1.5%, and that’s why a cotton shirt feels damp rather than slick when you sweat. Cotton also holds less odor. In a 2014 study, polyester shirts worn to a spin class smelled more intense and less pleasant than cotton ones, and odor bacteria grew almost only on the polyester.

Fabric choice is less likely to change your body temperature. A review of exercise studies found that fabric type didn’t measurably change thermoregulation in warm conditions. The difference you notice is in how the fabric feels against your skin and how it smells after a day’s wear.

What “100% cotton” means on a label

US rules let a label say “100% cotton” or “all cotton” only when the fabric is entirely cotton, with no tolerance. A blend can be off by up to 3 percentage points from its label, so a shirt marked 60% cotton could be 57%. The thread that holds the seams together and small structural trims aren’t counted, and that thread is often polyester. Elastic and decorative trim are excluded only if the label says so, as in “100% cotton, exclusive of elastic.”

“Combed cotton,” “Pima cotton” and “organic cotton” are descriptions added to the fiber name. They tell you something about the cotton, but the fiber is still cotton.