What is GSM? Fabric weight for t-shirts and hoodies
GSM means grams per square metre. It is the weight of one square metre of fabric, and it's the number factories use to talk about how heavy or thick a fabric is.
Choosing the right GSM is one of the biggest decisions for your garment. It changes how the piece feels, how it hangs on the body, how warm it is and how much it costs.
In this guide
What the number means
GSM in ounces
Typical GSM for each garment
What changes when GSM goes up
How to write GSM in your tech pack
How to check GSM yourself
Start with the right weight
What the number means
If a fabric is 260 GSM, a piece one metre by one metre weighs 260 grams. A higher number usually means a heavier, thicker fabric. A lower number means lighter and thinner.
Only compare GSM between similar fabrics. A knitted cotton jersey and a woven nylon can feel very different at the same number. Woven fabrics are tighter, so a thin nylon shell can be only 110–120 GSM and still be strong.
GSM in ounces
Some suppliers, mostly in the US, give fabric weight in ounces per square yard (oz). To change GSM to ounces, multiply by 0.0295.
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150 GSM ≈ 4.4 oz
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200 GSM ≈ 5.9 oz
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260 GSM ≈ 7.7 oz
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350 GSM ≈ 10.3 oz
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400 GSM ≈ 11.8 oz
Typical GSM for each garment
Every supplier draws the lines a little differently, but these ranges are a good starting point:
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Everyday t-shirts: about 150–200 GSM.
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Heavyweight t-shirts: from about 180–200 GSM upwards. Thick, boxy streetwear tees can be 240 GSM or more. Our free boxy tee uses 260 GSM cotton jersey.
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Fitted and stretch tops: lighter, so they sit close to the body. Our Y2K baby tee uses 190 GSM stretch jersey.
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Hoodies and sweatshirts: midweight is about 280–350 GSM. Heavyweight is 350–400 GSM or more. Our free cropped hoodie uses 400 GSM brushed fleece.
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Woven pieces like cargo pants, shorts and shell jackets: usually lower numbers than knits, because woven fabric is denser. Our ripstop cargo is 210 GSM and our nylon trail shorts are 110 GSM.
What changes when GSM goes up
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Feel and shape: heavier fabric has more body and holds a boxy shape. Lighter fabric is softer and drapes, so it hangs closer to the body.
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Warmth: heavier knits trap more air, which is why fleece hoodies are heavy.
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Price: more grams means more fabric, so the cost per garment goes up. Shipping weight goes up too.
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Season: light fabrics suit summer and hot places. Heavy fabrics suit autumn and winter.
How to write GSM in your tech pack
Step 1
Give a target and a range
Write the GSM you want and how far it can be off. Many factories work to about ±5%. For example: "260 GSM, accepted range 247–273 GSM". LineDrop templates show a range for every fabric.
Step 2
Say it's the finished weight
Washing, dyeing and finishing can change a fabric's weight, sometimes by 5–15%. Write "finished GSM (after washing/dyeing)" so the factory measures the fabric you will actually sell.
Step 3
Name the fabric too
GSM alone isn't enough. Add the fabric type and what it's made of, for example "heavyweight single jersey, 100% combed cotton" or "brushed-back fleece, 80% cotton / 20% polyester".
Step 4
Ask for a swatch first
Before the sample, ask the factory to send a small piece of the fabric (a swatch) with its GSM. Touching it is the fastest way to know if the weight is right.
How to check GSM yourself
Factories use a round GSM cutter that cuts exactly 100 cm² of fabric. Weigh the circle in grams and multiply by 100. For example, 2.6 g × 100 = 260 GSM.
Without a cutter, cut a 10 × 10 cm square (also 100 cm²) and weigh it on a small scale that shows 0.01 g. A kitchen scale that only shows whole grams isn't accurate enough, because 1 gram is already 100 GSM.
Start with the right weight
Every LineDrop template lists its fabric, GSM and a safe GSM range. In the customiser you can move the weight up or down in 10 GSM steps, and the PDF tech pack shows the new number for your factory. Our free tee and hoodie are a good place to start.