What fabric weight and GSM mean

Short answer: Fabric weight is measured in grams per square metre and abbreviated GSM. The number says how much fabric there is, and thus something about how thick and opaque the garment is.

What the number means

A higher number means more material per square metre. That makes the fabric thicker, heavier and more opaque.

Light qualities

Light fabrics are used for summer clothes and as a layer under other clothes. They are cooler but also more see-through.

Heavy qualities

Heavier fabrics are used for sweat pieces and for tops meant to be worn alone. See sweat clothing.

See-through

If a light t-shirt is see-through, it is nearly always the fabric weight and not the fibre that is the cause. See bamboo t-shirt for women.

Weight is not quality

A heavy fabric is not automatically better. A light quality with a good knit can last longer than a heavy one with a poor knit.

For bedding

For bedding the weight is rarely stated, but the weave means the same thing. See percale, jersey and sateen.

See also

More on the material in bamboo jersey.

Frequently asked questions

Is a higher GSM always better?

No. It simply means more fabric. For summer clothes, light is often better.

What decides how see-through it is?

Above all the fabric weight, not the fibre.

Where do I find the number?

It is not always stated. The description of whether the item is light or heavy usually says the same thing.