Why T-shirts shrink in the wash

Sep 12, 2026

Short answer: Fibres and knitted loops contract when exposed to heat and movement. The hotter the wash and the more tumble drying, the more the fabric shrinks, and most of it happens the first time.

Heat is the main cause

When yarn is spun and fabric is knitted, the fibres are stretched. At high temperatures they relax and pull back towards their original length, and the T-shirt gets smaller. For most fabrics 40 degrees is the limit, and that also applies to bamboo sweatwear. Go higher and the risk of shrinkage rises clearly.

The tumble dryer does the rest

Heat combined with mechanical movement is what shrinks fabric the most. In a tumble dryer, fabric is tossed around in hot air for a long time, and the loops pull tighter. Air drying removes that half of the problem entirely. That goes for every style in Copenhagen Bamboo bestsellers, thin or thick.

Most of it happens in the first wash

If the fabric has not been pre-shrunk at the factory, most of the shrinkage happens the first time it is washed. After that the size usually stays stable, as long as you keep the same temperature. That is why the first wash matters most. The same goes for long-sleeved styles, where the sleeves can get slightly shorter too.

Knitted fabric shrinks more than woven

T-shirts are almost always made of knitted fabric, where the yarn lies in loops. The loops can contract in both length and width, so a T-shirt shrinks more easily than a woven shirt. Often it loses most in length and gets a little shorter, while the width holds up better.

Viscose and cotton react differently

Fibres that absorb a lot of water, like cotton and viscose, swell in the wash and can contract as they dry. Synthetic fibres absorb less water and usually shrink less, but can be damaged by high heat. Bamboo viscose should therefore be treated gently, with a low temperature and a calm programme.

How to wash without shrinking

Wash at 30 or 40 degrees, turn the clothes inside out and choose a gentle programme with a low spin. Do not overload the machine, so the clothes are not pressed and twisted. Take them out as soon as the programme ends and hang them up straight away. That gives the fabric the best chance of keeping its size.

Dry flat or on a hanger

Hang the T-shirt to dry while damp and gently pull it into shape in length and width. Heavy sweatshirts dry best flat on a rack, so the weight of the water does not pull them out of shape. Do not dry on a radiator or in direct sun, as concentrated heat can act like a tumble dryer.

Read the care label

The label in the neck or side seam tells you what temperature and treatment the fabric can take. If it says 30 degrees, stick to that, even if the machine is full of other clothes at 40. If it says no tumble drying, that is exactly to prevent shrinkage. The label is the most precise guide you have.