What is a heavyweight t-shirt?

You bought it because it felt right in your hand. Thick, dense, the kind of cotton that holds its shape when you hold it up.

Eight months later it hangs off you. The hem has gone wavy, the collar sits wide, and in the right light you can see your singlet through the back.

A heavyweight t-shirt is one cut from denser, heavier fabric than an everyday tee, measured in GSM: grams per square metre, the mass of the fabric itself before anyone sews anything. Most everyday tees sit at 180 GSM or under.

Where "heavyweight" starts is less settled than the word suggests. There is no industry standard. Published guides put the line anywhere from 180 GSM to 300 GSM, depending on who is selling the blanks. So a tee can be called heavyweight by one brand and midweight by the next, at the same weight.

Ours is 300 GSM, 100% cotton. That clears every one of those lines.

The number is the whole reason the category exists. It is also, on its own, not enough — which is the more useful half of this answer.

What GSM actually measures

GSM measures fabric, not the garment.

It tells you how much cotton occupies a square metre before it is cut, sewn, washed or worn. It does not tell you how the shirt is built, how it was finished, or whether it will still fit after a summer of washes.

Two numbers get confused constantly, so it is worth separating them:

• GSM is fabric mass per unit area. It is fixed for the roll, and it is the number worth comparing.
• Garment weight is what the finished shirt weighs on a set of scales. It changes with size — a small and an XL cut from identical fabric weigh differently.

A brand quoting garment weight instead of GSM is not lying to you, but it is not answering the question either. If the figure arrives with a size attached, it is garment weight.

Why weight alone will not save you

Here is the part nobody selling heavy cotton wants to lead with: a heavy shirt that is built badly still goes out of shape. Weight buys you opacity and drape. It does not buy you a collar that holds, a hem that stays flat, or a body that fits the same in March as it did in November.

Three things decide that, and none of them is GSM.

Knit construction. Single jersey, the standard t-shirt knit, behaves differently at 300 GSM than a heavier interlock does at the same weight. Density is not the same as stability.

Finishing. Pre-shrinking — sometimes called compacting or sanforising — compresses the fabric before it is cut, so the garment does less of it later. It also adds weight: our own manufacturer confirmed pre-shrinking adds approximately 20 GSM. A pre-shrunk fabric and a raw one at the same stated GSM are not the same cloth.

Pattern. Whether shrinkage was engineered into the cut, or left for you to absorb. That is the difference between a tee that stays true to size and one that becomes a crop top in April.

What to check before you buy

Brand-agnostic. Apply it to us as readily as anyone.

Is the GSM published at all? Not "heavyweight", not "premium", not "substantial" — the number. If a brand will not put a figure next to the word, you are being asked to take an adjective on faith.

Are garment measurements listed per size? Chest, body length, shoulder. A size chart that stops at S/M/L tells you nothing about a trained build, which is exactly the fit that gets it wrong.

Is shrinkage stated? Every cotton tee moves. Roughly 3% is normal for a knitted fabric and is not a defect. What matters is whether the brand says so, and whether the pattern was adjusted to account for it.

What happens if it does not fit? Read the returns terms before you need them, not after.

Where we sit

Our tee is 300 GSM, 100% cotton. The shorts beside it in Drop 01 are 390 GSM.

The tee is not pre-shrunk. Expect approximately 3% at the first wash. The pattern was adjusted before cutting to absorb it, so it should still be true to size afterwards.

If it ever arrives feeling thin, or light, or fashion-led, we got it wrong and we want to know.

The short answer

There is no official line. Guides put heavyweight anywhere from 180 to 300 GSM. Ours is 300. But the number is a floor, not a finish — check the construction, the size chart and the shrinkage before you let a figure do your deciding for you.

Drop 01 lands in November.