GSM is grams per square metre. It is the weight of one square metre of the fabric, and it is the only number on a spec sheet that reliably tells you how a piece will behave.
A supermarket tee is somewhere around 140 to 180 GSM. A heavyweight tee starts around 250. Everything you can feel — whether light shows through it, whether it hangs or clings, whether it still has a shape in a year — tracks that number more closely than the price does.
The OVRS range, piece by piece
| Piece | GSM | oz/yd² | Composition |
|---|---|---|---|
| Washed Set, tee | 275 | 8.1 | cotton, garment-washed |
| Essential and Logo T-Shirt | 300 | 8.8 | 100% cotton |
| Washed Set, short | 320 | 9.4 | cotton, garment-washed |
| Essential Hoodie | 355 | 10.5 | 42% cotton / 58% polyester, brushed |
| Essential Relaxed Short | 420 | 12.4 | heavyweight cotton |
If you buy in ounces rather than grams, divide GSM by 33.9. A 300 GSM tee is an 8.8 oz shirt.
What the weight buys you
It stops being see-through
This is the one people notice first, and it only matters on light colours. A thin off-white tee shows whatever is underneath it the moment you step outside. At 300 GSM the cotton is dense enough that daylight does not go through it, which is the entire reason a light colour is wearable more than once.
It drapes instead of clinging
Light fabric follows your body because it has no weight of its own to fall with. Heavy fabric falls straight down from the shoulder. That is what makes an oversized cut read as deliberate rather than as a shirt that is too big — the pattern gives it room, and the weight makes it use that room.
It holds the shape you paid for
Dense cotton recovers. The collar goes back to round, the hem stays flat, the body does not stretch out across the chest and stay there. Thin cotton stretches permanently within a few washes, and the piece starts looking finished long before it wears out.
It survives more washes
More fibre per square metre means more material to lose before you can see it. Thin shirts go transparent at the shoulders and the elbows first, because those are the points that take friction. There is simply more to give at 300.
What the weight costs you
Heavier is not automatically better, and anyone telling you otherwise is selling weight rather than clothing.
- It is warmer. A 300 GSM tee is a real layer. In serious heat, a lighter shirt is the more sensible thing to wear.
- It takes longer to dry. Noticeably, if you do not use a dryer.
- It is stiffer at first. Dense cotton needs a few wears to soften. This is normal and it is not a defect.
- It costs more to make and to ship. More cotton per unit, more weight in the box.
The washed sets sit at 275 GSM rather than 300 for exactly this reason. They are garment-washed and cut to be worn as a whole outfit in warm weather, so the extra 25 grams would work against them.
How to check the tee you already own
You do not need a scale meant for fabric. Weigh the shirt on a kitchen scale, then work out its surface area — a size L tee laid flat is roughly 0.62 m by 0.75 m, doubled for front and back, so about 0.93 m². Divide the weight in grams by that number and you have a rough GSM.
Rough is enough. The difference between 160 and 300 is not subtle, and you will not need three decimal places to see which side of it your shirt is on.
Where the number stops mattering
Past about 400 GSM a tee stops being a tee. It gets stiff, it stops draping, and it starts behaving like a light jacket. Weight only helps up to the point where the piece still moves. Our shorts are 420 GSM because a short does not need to drape — it needs to hold a leg shape and not go limp. A shirt at that weight would just be uncomfortable.
So the useful question is not "how heavy is it". It is "is it heavy enough for what this piece has to do".
More: how to wash a heavyweight tee without losing the shape, and what oversized, boxy and regular fit actually mean.
Shop 300 GSM tees and 355 GSM hoodies.
