You're scrolling through a fabric listing and you see "320 GSM." Cool. What does that actually mean? Is it heavy? Light? Will it work for your hoodie idea, or is it going to feel like a paper towel?
GSM is one of those numbers that sounds technical, but it's actually the most useful spec on any fabric page. Once you know what to look for, you can pick the right fabric in about ten seconds. We put together this cheat sheet so you don't have to memorize anything. Bookmark it, screenshot it, send it to your friend who keeps buying the wrong weight.
What GSM actually means
GSM stands for grams per square meter. It's a measure of how much one square meter of that fabric weighs. Higher number, heavier fabric. Lower number, lighter fabric. That's it.
You'll also see weight listed in ounces per square yard sometimes. Same idea, different unit. A rough conversion: divide the GSM by 34 to get the oz/yd². So 340 GSM is about 10 oz/yd². Most listings on KBM show you both, so you don't have to do mental math.
One thing to know: GSM tells you weight, not feel. Two fabrics at the same GSM can feel completely different. A 200 GSM linen feels crisp and breathable. A 200 GSM jersey feels soft and stretchy. So GSM is your starting point, not the whole story. That's why ordering swatches is always a smart move before you commit to yardage.
The fabric weight chart
Here's the cheat sheet by weight range and what people actually use each one for.
Lightweight: under 150 GSM
Think voile, sheer linen, chiffon, gauze, lawn. These fabrics are barely there. You can see through them. They drape like water and weigh almost nothing.
What to make with it: summer blouses, scarves, linings, overlays, baby clothing, breezy dresses, anything you want to feel light and airy. If you're sewing a button-up shirt for hot weather, this is your zone.
Heads up: lightweight fabric is harder to sew. The fabric shifts, slips, and can get sucked into your machine. Use a fresh microtex needle, a walking foot if you have one, and take it slow.
Medium weight: 150 to 280 GSM
This is the everyday zone. Cotton jersey for t-shirts, light French terry, poplin, shirting, mid-weight linen, basic woven cottons. Most ready-to-wear lives in this range.
What to make with it: tees, basic shirts, summer pants, dresses, kids clothing, light pullovers. If you're sewing a wardrobe staple, you're probably reaching for a medium weight.
This is also the easiest weight to sew. The fabric is stable enough to handle without fighting you, but not so thick that seams get bulky.
Sweatshirt weight: 280 to 450 GSM
Now we're getting into the good stuff. This is the range where French terry, fleece, and heavyweight jersey live. It's the streetwear sweet spot.
What to make with it: hoodies, crewnecks, sweatpants, joggers, premium tees that have real body, structured tote bags. Our 450 GSM French terry is one of our top sellers because it hits that "this actually feels like the hoodie I always wanted" weight without crossing into stiff territory.
If you're trying to match the feel of a vintage Champion sweatshirt or a current-era Fear of God hoodie, you want something in the 380 to 450 range. Anything lighter and it feels like a long-sleeve tee.
Heavyweight: 450 to 600 GSM
This is real heavy. Heavy fleece, heavy French terry, canvas, twill, mid-weight denim. The fabric has presence. You feel it on your shoulders when you put a hoodie on.
What to make with it: premium hoodies, heavyweight joggers, structured outerwear, bags, work shirts, jackets, tote bags that won't collapse. If you've been seeing those super thick sweatshirts trending and wondering how to get that look, this is the weight.
Sewing tip: switch to a heavier needle (a 90/14 or 100/16 universal, or a denim needle for canvas and twill). Your regular needle will bend or skip.
Super heavyweight: 600+ GSM
This is loftwear. Premium hoodies that feel like a blanket. Heavy denim. Duck canvas. Wool melton. The Carhartt-meets-Yeezy zone.
What to make with it: super premium fleece pieces, heavy denim jackets and jeans, structured bags and totes, workwear, upholstery, anything where weight equals luxury or durability.
Our 650 GSM French terry is honestly the heaviest knit we carry, and it shows up in some pretty high-end small batch streetwear runs. Fair warning: pressing seams flat takes patience, and your machine has to be in good shape to feed it without skipping.
Wovens are a little different
For knits like jersey and French terry, the GSM range we talked about is pretty universal. But wovens (denim, canvas, twill, oxford) play by slightly different rules. A 200 GSM woven feels heavier in the hand than a 200 GSM knit because the structure is denser and less stretchy.
Quick woven cheat sheet:
Light shirting: 100 to 160 GSM. Soft button-ups, summer shirts.
Mid shirting and bottomweight: 160 to 280 GSM. Pants, chore coats, light denim.
Heavy denim and canvas: 280 to 450 GSM. Jeans, workwear, jackets, bags. Selvedge denim usually sits between 330 and 450.
Super heavy: 450+ GSM. Heavy duck, upholstery, workwear that lasts forever.
How to pick the right weight by garment
If you're not sure where to start, match the weight to the garment:
Light summer top or scarf: 80 to 150 GSM
Basic t-shirt: 160 to 220 GSM
Premium heavyweight tee: 220 to 280 GSM
Light hoodie or pullover: 280 to 350 GSM
Standard hoodie or crewneck: 380 to 450 GSM
Premium heavyweight hoodie: 450 to 600 GSM
Selvedge jeans: 330 to 450 GSM
Heavy denim jacket: 380 to 500 GSM
Canvas tote: 280 to 400 GSM
Workwear or chore coat: 350 to 500 GSM
Quick FAQ
Is higher GSM always better?
No. Higher just means heavier, not better. A 600 GSM French terry hoodie is amazing for fall. A 600 GSM summer tee would be unwearable in July. Match the weight to the season and the garment.
Does GSM affect shrinkage?
Not directly. Shrinkage depends on the fiber and whether the fabric is pre-shrunk or sanforized. But heavier fabrics tend to shrink more in absolute terms because there's more material to begin with. Always pre-wash before you cut.
How do I know the GSM of fabric I already own?
Cut a 10cm by 10cm square, weigh it on a kitchen scale in grams, and multiply by 100. That gives you the GSM. It's also a fun trick to confirm a listing.
Try before you buy
Reading specs is one thing. Feeling the fabric in your hand is another. We sell swatch packs so you can compare weights side by side before you commit to yards. Order a few swatches from the weights you're considering and you'll know exactly what 300 GSM feels like versus 450 GSM.
Making bigger drops or running a small brand? Hit our wholesale page for pricing on quantities.
Got questions on a specific weight? Email us at support@kbmfabrics.com. We answer within a business day and we're happy to point you in the right direction.