This is the most expensive misunderstanding in hospitality linen, and it takes two minutes to clear up.

What GSM measures

Grams per square metre. The mass of a square metre of the fabric. Nothing more.

It is a genuinely useful number when you are comparing two otherwise identical constructions, and it is close to meaningless on its own.

Why two robes at the same GSM differ

Mass can be put into a fabric in different places. A long loose loop puts it into height; a short dense loop puts it into how many loops there are per square centimetre.

The dense one usually absorbs faster and dries slower. The loose one feels thicker in the hand and crushes flatter with use. Same number, different garment.

Fibre matters as much

Cotton staple length decides whether the loop sheds. A short-staple yarn produces lint and a loop that flattens; a longer staple holds up through hundreds of cycles.

This is also why a cheap high-GSM robe can look worse after six months than a mid-weight one made properly.

What to ask for instead

Ask for GSM, loop length, loop density and staple length, and ask whether the dimensions quoted are pre-wash or post-wash. Five short answers.

A supplier who can give you all five is describing a product. One who can only give you GSM is describing a price.