Why do my t-shirts shrink and how do I prevent it?

T-shirts shrink because of heat, mostly during washing and drying. When cotton fibres are exposed to hot water and high-temperature tumble drying, they contract. Cold wash and air dry prevents most of this. Pre-shrunk fabrics shrink less but still respond to heat.

What actually happens

Cotton is stretched during manufacturing as it is knitted into fabric and again as it is cut and sewn. That tension stays in the fibres. When you wash the garment in hot water or tumble dry it on high heat, the fibres relax back toward their natural length, which means the garment shrinks.

Most shrinkage happens on the first wash. After that, each subsequent wash adds a small amount until the fabric is fully relaxed, usually within five or six washes if you use heat.

How to prevent it

Cold water wash. Air dry or low-heat tumble dry. Skip the high-heat ironing. These three habits together prevent almost all shrinkage on most cotton tees.

If you must use a dryer, pull the garment out while it is still slightly damp and let it finish on a hanger. The last 10 percent of drying is where the most shrinkage happens.

Pre-shrunk fabric

Many tees are sold as pre-shrunk, which means the fabric was washed and dried under controlled conditions before being cut. This reduces shrinkage at home but does not eliminate it. Hot wash and high-heat dry will still shrink pre-shrunk fabric, just less.

What about poly blends

Cotton-poly blends shrink less than 100% cotton because polyester does not respond to heat the same way. A 60-40 cotton-poly tee will hold its shape through hot washes better than pure cotton, but still wash cold for the print, the colour, and the longevity of the garment.

If it has already shrunk

You can sometimes recover a small amount of size by soaking the tee in lukewarm water with hair conditioner for half an hour, then gently stretching it while damp and air drying flat. It rarely fully reverses, but it helps.