· 4 min read
What Is GSM in Fabric? A Weight Guide for T-Shirts, Hoodies and Sportswear
GSM means grams per square metre: the weight of one square metre of fabric. T-shirts usually run 140–300 GSM and hoodies 280–500 GSM; higher numbers mean heavier, thicker, more structured fabric. This guide gives the ranges for each garment, converts GSM to ounces, and explains what GSM does and does not tell you about quality.
In short
GSM means grams per square metre: the weight of one square metre of fabric. T-shirts usually run 140–300 GSM and hoodies 280–500 GSM; higher numbers mean heavier, thicker, more structured fabric. This guide gives the ranges for each garment, converts GSM to ounces, and explains what GSM does and does not tell you about quality.
The short answer: GSM stands for grams per square metre — the weight of a one-metre by one-metre piece of fabric. A standard T-shirt is 150–180 GSM and a heavyweight one is 220–300 GSM. A standard hoodie is 280–330 GSM and a heavyweight one is 400–500 GSM. Higher GSM means a heavier, thicker, more structured fabric, but it does not by itself mean better quality: yarn, knit and finishing matter just as much.
What does GSM measure?
GSM is fabric density by weight. A circular cutter punches out a disc of fabric with a known area, the disc is weighed, and the result is scaled to one square metre. Because it is a weight per area, GSM is independent of garment size: a small and an XXL hoodie cut from the same fleece have the same GSM.
In the United States fabric weight is often given in ounces per square yard instead. To convert, divide GSM by 33.9.
GSM to ounces conversion
| GSM | oz per sq yd | Typically used for |
|---|---|---|
| 140 | 4.1 | Lightweight tees, sportswear |
| 160 | 4.7 | Standard tees |
| 180 | 5.3 | Standard to midweight tees |
| 200 | 5.9 | Midweight tees, polos |
| 240 | 7.1 | Heavyweight tees |
| 280 | 8.3 | Very heavy tees, light sweatshirts |
| 320 | 9.4 | Standard hoodies and sweatshirts |
| 380 | 11.2 | Heavy hoodies |
| 450 | 13.3 | Heavyweight streetwear hoodies |
| 500 | 14.7 | Very heavy, structured hoodies |
What GSM should a T-shirt be?
| Weight class | GSM | Character | Good for |
|---|---|---|---|
| Lightweight | 130–150 | Thin, drapey, breathable | Hot climates, giveaways, athletic tops |
| Standard | 160–180 | The everyday tee | Merchandise, uniforms, most brands |
| Midweight | 190–210 | Slightly structured, more opaque | Premium basics |
| Heavyweight | 220–300 | Dense, boxy, holds its shape | Streetwear and oversized fits |
For oversized and boxy streetwear cuts, 220 GSM and above is usual, because a lighter fabric collapses instead of holding the silhouette. Browse custom T-shirts and polos for the styles we make.
What GSM should a hoodie be?
| Weight class | GSM | Character | Good for |
|---|---|---|---|
| Lightweight | 240–280 | Layering weight | Spring ranges, gym cover-ups |
| Standard | 300–350 | The typical retail hoodie | Teams, merchandise, all-season wear |
| Heavyweight | 380–450 | Thick, structured, warm | Streetwear, premium labels |
| Super heavyweight | 480–500+ | Stiff, very warm, stands up on its own | Statement pieces, winter drops |
SeamFoundry makes custom hoodies in 300, 350, 400, 450 and 500 GSM fleece, in brushed or loopback finishes. See fleece vs French terry for the difference between the two.
What GSM do other garments use?
| Garment | Typical GSM |
|---|---|
| Sublimated football or basketball jersey | 130–160 |
| Polo shirt (piqué) | 180–220 |
| Leggings and compression wear | 220–300 |
| Joggers and sweatpants | 280–400 |
| Tracksuit (polyester tricot) | 220–280 |
Does higher GSM mean better quality?
No. GSM tells you weight, not quality. Two 400 GSM fleeces can feel completely different depending on:
- Yarn — combed, ring-spun cotton is smoother and stronger than carded, open-end yarn at the same weight.
- Fibre blend — 100% cotton feels and ages differently from an 80/20 cotton-polyester blend.
- Knit tightness — a tight knit holds shape and resists pilling; a loose one bags out.
- Finishing — pre-shrinking, enzyme washing and brushing change both hand-feel and how the garment behaves after washing.
A well-made 320 GSM hoodie will outlast a poorly made 450 GSM one. Heavier fabric also costs more, in fabric and in shipping, because couriers charge by weight and volume.
How does GSM affect price and shipping?
Fabric is bought by weight, so a 450 GSM hoodie uses roughly 40% more material than a 320 GSM hoodie of the same size, and costs more to ship. If your budget is tight, moving from 450 to 400 GSM is often invisible to the customer and noticeable in your margin. The low-MOQ hoodie guide shows how weight feeds into unit price.
How do you check the GSM you were sold?
- Ask for the GSM in writing in the quote and on the spec.
- Weigh the sample. A size L hoodie in 450 GSM fleece is noticeably heavier in the hand than one in 320 GSM; a kitchen scale will show the difference between two samples.
- Allow a tolerance. Knitted fabric varies by a few percent from batch to batch, so a small difference from the stated figure is normal.
- Check it on the pre-production sample, not after bulk has been made.
Choosing a weight for your order
If you are unsure, tell us the garment, the fit and the climate your customers live in, and we will recommend a weight and send fabric options with your quote. Request a quote and you will hear back within 24 hours. The glossary has short definitions of GSM and other production terms.
