If you've ever shopped for fabric online and seen a number like "180 GSM" or "320 GSM" stamped next to a listing, you've already met one of the most useful — and most overlooked — specs in the textile world. At our mill in Los Angeles, GSM is the first number we look at before we even touch a swatch. Here's why it matters, and how to read it like a pro.
What is GSM?
GSM stands for grams per square meter. It's exactly what it sounds like: take a piece of fabric one meter by one meter, weigh it, and the number you get is its GSM.
Why use weight instead of thickness? Because thickness is misleading — a chunky loose-knit sweater can be "thicker" than a tightly woven canvas while weighing half as much. GSM gives you an honest, apples-to-apples way to compare fabrics across different fibers and constructions.
In the US you'll sometimes see weight expressed in ounces per square yard (oz/yd2). The conversion is roughly 1 oz/yd2 = 33.9 GSM. So a "10 oz" denim is about 340 GSM.
Why Fabric Weight Matters
GSM tells you three things at a glance:
- Drape — lighter fabrics flow and gather; heavier fabrics hold structure.
- Opacity — lower GSM jerseys often need a lining or layering.
- End use — a 140 GSM jersey makes a beautiful summer tee, but it'll feel flimsy as a hoodie.
If you match the weight to the project, your garment will hang and wear correctly. If you don't, no amount of skilled sewing can save it.
Light, Medium, and Heavy: A Quick Rule of Thumb
For knit fabrics, here's the cheat sheet we give new customers:
| Weight Category | GSM Range | Typical Use |
|---|---|---|
| Ultra-light | Under 130 | Lining, sheer overlays, baby wear |
| Light | 130–180 | T-shirts, summer dresses, scarves |
| Medium | 180–260 | Long-sleeve tees, light sweatshirts, leggings |
| Heavy | 260–360 | Hoodies, sweatpants, structured dresses |
| Extra heavy | 360+ | Premium sweatshirts, outerwear, upholstery |
These ranges overlap because fiber content and knit structure matter too. A 220 GSM cotton interlock feels denser than a 220 GSM rayon jersey — same weight, very different hand.
GSM by Fabric Type
Jersey
Cotton and blended jersey is the workhorse of the knit world. Standard ranges:
- Lightweight jersey: 120–150 GSM — great for drapey tees and summer layering pieces.
- Mid-weight jersey: 160–220 GSM — the classic t-shirt and bodysuit weight.
- Heavy jersey: 230–280 GSM — premium streetwear tees, henleys, and structured dresses.
French Terry
Our French terry and cotton fleece collection runs from about 240 GSM up to a serious 450 GSM heavyweight. Lightweight French terry (240–280) is perfect for spring crewnecks. Heavy terry (380+) is what you want for a premium gym-rat hoodie that drapes and lasts.
Fleece
Brushed fleece typically lives in the 280–400 GSM range. The brushing fluffs up the loop side, which adds loft and warmth without much extra weight.
Denim
Woven, but worth a mention since people ask. Light denim (chambray) sits around 4–7 oz (135–235 GSM), standard jeans are 10–12 oz (340–400 GSM), and rigid selvedge can hit 14+ oz (475+ GSM).
How to Use GSM When You Shop
Before you click "add to cart," ask yourself:
- What's the garment? Match it to the table above.
- How will it drape? Read GSM together with the fiber blend. Modal and rayon drape softer than cotton at the same weight.
- What's the season? A 280 GSM tee will feel like a tank in January and a furnace in July.
If a listing doesn't show GSM, that's a small red flag. Reputable mills publish it because we know our customers need it.
Shop the Fabrics Mentioned
- Jersey collection — 120 to 280 GSM
- French terry and cotton fleece — 240 to 450 GSM
- All fabrics — browse everything by weight
Once you start reading GSM, you'll never go back to guessing by photo. It's the single fastest way to predict how a fabric will feel and behave before it ever touches your cutting table.