What gsm means on a fabric

Sep 12, 2026

Short answer: GSM stands for grams per square metre. The number tells you how thick and full a fabric is, and it is the most useful figure for comparing clothes when you shop online and cannot feel the fabric first.

What the number measures

GSM is the weight of one square metre of fabric, in grams. The more grams, the more material there is, and the thicker and fuller it usually feels. So the number tells you about the amount of fabric, not how it is made. That makes it easy to compare two items you cannot hold in your hand.

The number in practice

As a rule of thumb, fabric under 160 gsm is thin, 160 to 250 is medium, and over 250 is thick sweatshirt fabric. Thin fabric is light and airy and suits warm days or wearing as a base layer. Most everyday tops sit in the medium range. See bamboo underwear for women.

What the number does not tell you

GSM says nothing about yarn quality, how the fabric is knitted or how long it lasts. Two fabrics with the same number can feel completely different, because the yarn and the knit differ. A light fabric can wear well, and a heavy one can pill quickly. Use the number to judge thickness, not quality. See bamboo panties.

How to use it

Only compare gsm between items of the same type. Underwear and a hoodie cannot be compared, because they are made for different purposes. Instead, look at two tops or two pairs of panties and see which has the higher number. Then you know which feels thicker and which is lighter. See bamboo tops for women.

Thin fabric for warmth and layers

A low gsm gives a light fabric that feels cool and sits close to the skin without bulk. It works well for summer, sleepwear and layers under other clothes. On the other hand, very thin fabric can be more see-through in light colours. If you want something light, a darker colour is often a good choice.

Thick fabric for cool days

A high gsm gives a heavier fabric that holds warmth better and drapes more calmly on the body. It suits sweatshirts, hoodies and trousers for cooler days. Indoors, though, a thick fabric can feel too warm if you get cold in the morning but sit in a warm office. A medium fabric in layers is then often more practical.

The number is not always listed

Many shops do not list gsm, so you need other clues. Look in the description for words like light, full or thick, and check the photos to see whether the fabric falls softly or stands away from the body. If in doubt, ask the shop. It is a normal question, and the number says more than the word soft.

Feel the fabric after washing

A fabric can change a little after the first few washes. Some fabrics draw in slightly and become a bit denser, while others turn softer. This does not change much how thick it feels, but it can change how it drapes. Wash at a low temperature and dry flat, so the fabric keeps its shape and body longest.