GSM
Grams per square metre — the standard measure of fabric weight.
GSM tells you how heavy a square metre of fabric is. It is the first number to fix when specifying a fabric, because it drives drape, opacity, durability and cost.
A 140 gsm cotton and a 240 gsm cotton are different products even when the composition matches. Always ask whether the figure is for greige or finished fabric, and what tolerance the mill works to.