Fabric weight in t-shirts is measured in GSM (grams per square meter) — the higher the number, the thicker and denser the fabric.
Light cotton sits around 140–160 GSM, midweight hovers near 180–200 GSM, and heavyweight begins at 200 GSM and above.
At the extreme end, ultra-heavy tees can reach 250–270 GSM, giving a weighty, almost sweatshirt-like feel. These are the thickest cotton t-shirts you can buy.
But it’s not just weight that matters — it’s the weave and yarn quality too. A tightly knitted jersey from long-staple cotton can feel even denser and more luxurious than a loosely woven fabric of the same GSM.