Every clothing brand now calls its tees heavyweight. The word has been stretched to cover everything from a slightly thicker undershirt to a garment that could stop a light breeze on its own. There is a number that settles it, and it takes about a minute to learn.
GSM is weight per area
GSM stands for grams per square meter. Cut a one-meter square of the fabric, put it on a scale, and that reading is the GSM. Higher means denser, thicker cloth. It says nothing about the size of the shirt, only about the material it's made from.
American mills often quote ounces per square yard instead. To convert, divide GSM by roughly 34. A 200 GSM fabric is about 5.9 ounces.
Where the lines are
| Weight | GSM | Ounces | What it's like |
|---|---|---|---|
| Lightweight | Under 150 | Under 4.4 | Thin, drapey, a little sheer in white. Good in real heat. |
| Midweight | 150 to 200 | 4.4 to 5.9 | The standard everyday tee. Most band and promo shirts. |
| Heavyweight | 200 to 280 | 5.9 to 8.3 | Structured and opaque. Holds its shape and its collar. |
| Extra heavy | 280 and up | 8.3 and up | Closer to a light sweatshirt. Stands away from the body. |
These bands are convention, not law. The apparel trade generally starts calling a tee heavyweight at around 6 ounces, which is about 200 GSM. For reference, a basic bulk blank like the Gildan 5000 is 5.3 ounces, and Shaka Wear's well-known heavy tee is 7.5.
What the weight changes
- Drape. Light fabric follows the body. Heavy fabric hangs from the shoulders and keeps its own outline, which is why boxy cuts are almost always made in heavier cloth.
- Opacity. A white tee under about 180 GSM tends to show what's beneath it. Above 200, it generally doesn't.
- The collar. Thin ribbing stretches and waves after a few washes. A dense collar on a dense body stays flat.
- The print. Ink sits on a tighter, smoother surface. Fine lines stay fine, which matters for the kind of detailed illustration we do.
- Lifespan. More cotton takes longer to wear through. A heavy tee tends to soften over the years instead of thinning out.
When heavier is not better
Weight is a tradeoff, and any brand that says otherwise is selling something. A 300 GSM tee in a Central Valley August is a bad afternoon. Heavy cotton holds more water, so it dries slowly after a wash or a workout. And a very heavy tee in a slim cut can feel stiff rather than substantial.
Weight alone doesn't make a shirt good, either. Fiber quality, how the yarn is spun, and how the garment is finished all matter. Two 240 GSM tees can feel completely different in the hand.
For San Francisco, though, heavy is close to ideal. The temperature rarely leaves the 50s and 60s, the wind is constant, and your tee is often your only layer for part of the day. A dense one does real work. We go deeper on that in our layering guide to the city.
What we use at Fog & Form
Every Fog & Form garment sits in the heavyweight range or above. By cut:
- Seamless and boxy tees: 230 GSM
- Enzyme washed tees: 250 GSM
- Baby tees: 200 GSM
- Long sleeves: 305 GSM
- Hoodies: 350 GSM fleece
- Sweatshirts: 360 GSM
Every piece is printed in the USA using direct-to-garment printing, which lays ink into the fibers and suits high-detail artwork.
We chose heavier cloth for a plain reason. Each design in the catalog documents something that lasted, whether that is a tower, a streetcar line or a neighborhood. Printing it on a shirt that gives out in a year would miss the point.
Start with T-Shirts for the full range, Essentials for the pieces that carry only our mark, or Long Sleeves and Hoodies for the upper end of the scale.
How to keep one for ten years
- Wash cold, inside out. It protects the print and the color.
- Skip the high-heat dryer. Tumble low or hang dry. Heat is what shrinks cotton and cracks ink.
- Don't hang heavy tees on thin wire hangers. The weight pulls the shoulders out of shape. Fold them.
- Leave the bleach and fabric softener out.
Quick answers
What GSM is considered heavyweight for a t-shirt?
Around 200 GSM and above, which is about 6 ounces per square yard. Premium heavyweight tees commonly fall between 240 and 300 GSM.
Is a higher GSM always better?
No. Higher GSM means thicker, more durable fabric, but it is also warmer and slower to dry. The right weight depends on climate and fit.
How do I convert GSM to ounces?
Divide GSM by 33.9 to get ounces per square yard. 240 GSM is about 7.1 ounces.
Do heavyweight t-shirts shrink?
Any cotton can shrink with heat. Washing cold and drying on low or on a line keeps shrinkage minimal.