Does Polyester Shrink? What Heat Does to Polyester and Blends

You pulled a performance tee out of the dryer and it looks smaller. Did the polyester shrink, or is it the cotton in the blend?

The short version: polyester holds its size far better than cotton, rayon or wool, and what little it can shrink comes from heat, not water. Below are the temperatures that matter, how common blends behave, and what this means if your shirts carry a printed logo.

By the RELYmedia editorial team · Updated November 2, 2026

Why Polyester Resists Shrinking

Most apparel polyester is polyethylene terephthalate (PET), the same polymer used in plastic drink bottles. It is melted, spun into fibers, then knit or woven into cloth. The fibers absorb very little water, so they do not swell and relax in the wash the way cotton fibers do. That swelling and relaxing is what makes cotton shrink.

PET is also thermoplastic: heat softens it and cooling locks it in a new shape. According to the PET reference data, the polymer starts to soften (its glass transition) at roughly 67 to 81 °C (153 to 178 °F) and melts above about 250 °C (482 °F). Mills use that behavior on purpose. They heat-set polyester fabric under tension at high temperature so the fibers remember that size.

A cold or warm wash never gets near that point. A very hot dryer drum, a hot iron or a heat press can, and that is where the small amount of shrinkage people notice comes from.

When Polyester Does Shrink

Water alone will not shrink polyester. Heat does the damage, and the closer it gets to the fiber’s softening range, the more risk you take.

Past a point the problem is no longer shrinkage. Polyester that gets too hot can glaze (turn shiny), pucker or melt, and that damage cannot be undone.

Check a Garment Yourself

Shrinkage varies by knit, finish and blend, so the reliable answer for a specific shirt is to measure it. This is a simplified version of how textile labs check dimensional change:

1. 1Lay the shirt flat and measure chest width (armpit to armpit) and body length (high point of the shoulder to the hem).
2. 2Wash and dry it on the settings you actually plan to use.
3. 3Let it cool and rest flat for a few minutes, then measure the same two points again.
4. 4Divide the change by the original measurement and multiply by 100 to get the percent of shrinkage.

Repeat after three to five cycles if you want a fair picture, because some garments relax or shrink a little more over the first few washes.

Do Polyester Blends Shrink? (Cotton, Spandex & More)

Most printed tees and hoodies are blends, and blends behave differently because the other fiber changes the result.

Cotton-Polyester Blends

The cotton content shrinks, not the polyester. More cotton means more potential shrinkage, so a blend lands somewhere between the two fibers. The table ranks common blends by cotton share. It is a relative guide, not a measured percentage.

Polyester-Spandex & Elastane Blends

Spandex (also sold as Lycra or elastane) adds stretch. A common mix is 95% polyester and 5% spandex. These blends hold their size well, but high heat breaks down spandex over time, so the garment can lose its snap-back and look baggy. Cool washes and low or no dryer heat protect it.

Polyester-Rayon Blends

Rayon is semi-synthetic and shrinks much more readily than polyester. A polyester-rayon blend shrinks more than pure polyester but less than pure rayon. When in doubt, air dry.

Recycled polyester is the same PET polymer as virgin polyester, so it responds to heat the same way. Care for it exactly like standard polyester.

How to Shrink Polyester on Purpose (If You Want To)

If a polyester shirt runs big, heat is the only lever, and the change you get is small and hard to predict.

1. 1Wash in the hottest water the care label allows.
2. 2Tumble dry on high for a full cycle.
3. 3Check the fit and measure. Repeat once at most.

Do not try to force it with an iron or a heat press. You are far more likely to glaze or melt the fabric than to take off a size. If the garment is a blend, most of whatever shrinkage you get will come from the cotton or rayon.

How to Wash & Dry Polyester So It Keeps Its Shape

Start with the care label. In the US, the FTC’s Care Labeling Rule requires the label to warn you when regular hot water, a hot dryer or a hot iron would harm the garment, so a “tumble dry low” line is there for a reason.

Washing Polyester

Drying Polyester

• Use low heat (one dot on the tumble-dry symbol) or the air-dry setting.
• Avoid high heat. It is the most common cause of shrinkage and glazing.
• Hang drying is safest, and polyester dries quickly anyway.
• Remove promptly so the garment does not sit in a hot drum.

Ironing & Steaming Polyester Safely

The dots on an iron symbol stand for maximum soleplate temperatures: one dot is 110 °C (230 °F), two dots 150 °C (302 °F) and three dots 200 °C (392 °F), according to the care symbol system used on labels. Polyester belongs on the one or two dot (synthetic) setting, with a press cloth between the iron and the fabric, and never directly on a print. A garment steamer releases wrinkles without the melt risk.

Polyester vs. Cotton, Wool & Other Fabrics

Cotton shrinks more than polyester because its fibers absorb water and swell. Wool can felt and shrink badly with heat and agitation. Rayon and linen also move more in the wash. Polyester is the most size-stable of the common apparel fibers, which is why it dominates athletic and team wear.

PET was patented in 1941 by John Rex Whinfield and James Tennant Dickson of the Calico Printers’ Association in Manchester, England, and DuPont began producing its Dacron polyester fiber in the US in 1950.

What This Means for Printed Polyester Apparel

Because polyester holds its size, a printed logo stays where you put it and a team’s shirts still fit after a season of washing. The bigger risk with polyester is not shrinkage but heat during decoration.

Dye Migration

On polyester, poly-cotton blends and tri-blends, too much heat at the flash, cure or post-cure stage can make the fabric’s dye gas off into the ink. A white or light logo on a red or dark polyester shirt then turns pink or gray, and the change is permanent. SanMar’s decorator white paper on dye migration recommends low-cure inks with bleed-blocking properties, which generally cure at 290 to 320 °F and some as low as 250 °F, plus a gray or black blocker base when migration is aggressive and letting garments cool before stacking them.

The Best Printing Method for Polyester

Dye sublimation turns the ink into a gas that bonds with the polyester fibers, so the design becomes part of the fabric and will not crack or peel. It only works on high polyester content and light colors. For dark or blended shirts, screen printing with low-cure ink or a DTF transfer is the usual choice. Browse custom athletic wear for polyester performance shirts that take these methods well.