What GSM Actually Means
, 3 min Lesezeit
GSM is grams per square metre — the one honest number in clothing. What 220, 250, 280, 320, and 400GSM actually feel like, and what counts as a normal t-shirt weight.
Fabric weight is the most honest spec in clothing, and almost nobody explains it. 250GSM. 270GSM. 400GSM. 420GSM. Here is what the numbers mean.
GSM, defined
GSM is grams per square metre — the weight of one square metre of fabric, on a scale. That's the whole definition. No marketing lives inside it. A higher number means more material in every inch: thicker hand, more structure, more opacity. For a t-shirt, it is the weight spec that matters. Garment weight in grams changes with size; GSM does not.
What is a normal t-shirt GSM?
160–200GSM. That is the standard retail tee: most mall and fast-fashion shirts live here. It is fine, and it is forgettable. Below 160GSM the fabric turns semi-sheer and the hem curls within a month of washes.
The scale, with reference points
- 120–160GSM — promotional tees and undershirts.
- 160–200GSM — the standard. Normal t-shirt weight.
- 200–250GSM — where "heavyweight" honestly begins. The shirt holds its shape on its own.
- 250–320GSM — true heavyweight. Boxy silhouettes work here because the fabric can stand, not cling.
- 320GSM and up — tee territory ends and fleece begins. Hoodies and sweats live here. A 420GSM hoodie carries more than double the fabric of a 180GSM tee.
What each weight feels like
220–230GSM. The first step above standard. Opaque, holds a collar, still drapes. Entry-level heavyweight, and the point where the number on the label starts to matter.
250–280GSM. Stands off the body. Boxy and oversized cuts keep their shape, and the fabric softens with wear instead of thinning.
300–320GSM. Stiff when new, soft after a few washes. Dense enough that it reads as structure, not just a shirt. Warm in summer.
400–420GSM. Fleece and French terry weight. Hoodies, sweatshirts and sweatpants. Built to hold a silhouette for years.
Why weight changes everything
Weight decides how a shirt hangs: light fabric clings and creases, heavy fabric falls straight and holds a silhouette. It decides opacity — no undershirt logic. And it decides lifespan, because more fibre survives more washes. A heavyweight tee fades and softens with age. A light tee warps and thins.
What GSM doesn't tell you
Weight is necessary, not sufficient. Yarn quality matters: combed, fine-count cotton at 235GSM wears smoother than coarse yarn at the same weight. Fibre matters too. GSM measures fabric, not material, so 270GSM of a cotton-polyester blend will not behave like 270GSM of pure cotton. Knit density and finish — a sunfade, a snow wash, hand-distressing — change how identical weights feel. Read the weight and the fibre content.
"Heavy cotton" and "midweight" are not measurements
Neither term has a fixed number behind it. "Midweight" usually points at the band between standard and heavyweight, roughly 180–220GSM, but sellers use it loosely. "Heavy cotton" on a label is a description, not a spec. If a listing says "thick" or "quality cotton" and won't publish a weight, that is the answer.
Ounces to GSM
Some listings use ounces per square yard. Multiply by 33.9 to get GSM. The Kanji Dragon Wave Striped Soccer Jersey is 5.6 oz/yd², about 190GSM. The Shinsei Essential Heavyweight Hoodie is 11.8 oz, which is the same 400GSM.
The ladder, in pieces you can order
- 250GSM — Kanji Dragon Sunfade Tee: hand-scrunched finish on a true heavyweight base.
- 270GSM — Shinsei MU Void Hooded Tank: 87% cotton, 13% polyester, snow-washed.
- 400GSM — Shinsei Essential Heavyweight Hoodie: fleece weight, oversized fit.
- 420GSM — Shinsei Wide-Leg French Terry Sweatpants: double waistband, built for years.
How to check before you buy
Look for the number in the product specs, then check the fibre content next to it.
Weight is the spec. Everything else is the mark. Start with Kanji Dragon or Shinsei.