What Does GSM Mean in Fabric? The Weight Number Explained

Here's the quick answer: GSM means grams per square metre — literally how much one square metre of the fabric weighs. It's the number that tells you whether a fabric is floaty, medium or hefty before you ever touch it: under 130gsm is lightweight, 130–250 is the everyday middle, over 250 is heavyweight. Online fabric shopping becomes far less of a gamble once you can read it.

The ladder, with fabrics you know

60–130gsm — the floaters: chiffon, voile, lightweight viscose. Summer dresses, floaty sleeves, linings, scarves. Light passes through; drape is everything.

130–250gsm — the everyday middle: poplin and quilting cotton (~110–150), most jerseys (~160–220), ponte and scuba entering the upper end. Shirts, dresses, T-shirts, trousers — most of a wardrobe lives here.

250gsm+ — the heavies: sweatshirt fleece, denim, corduroy, coating fabrics, upholstery. Structure, warmth, and garments that hold a silhouette.

What GSM tells you — and what it honestly doesn't

It tells you weight, and by proxy: opacity (heavier usually = less see-through), warmth, and how much structure a garment will hold. It does not tell you drape or stretch — a 200gsm scuba and a 200gsm denim weigh the same and behave like different animals, because one is a springy knit and one a rigid woven. GSM is one axis of a fabric's personality, not the whole character. (For the knit/woven axis, the ten-second test.)

How to actually use it when shopping

Match the number to the destiny: a floaty summer dress wants 80–150gsm; a structured shift dress 200–300; a hoodie 280+; curtains and cushions heavier still. And the pattern envelope's fabric suggestions quietly encode a GSM range — "lightweight wovens" means under ~150, "medium-weight" the middle band. When in doubt between two weights for a garment, the lighter one drapes more forgivingly.

The hand-check when numbers aren't enough

GSM narrows the shortlist; fingers make the final call. That's what samples are for — £1.49 turns "180gsm viscose jersey" from a specification into a feeling. Number first, hand second, metres third: the online fabric-buying ritual that never disappoints.