What is a heavyweight t-shirt?
A heavyweight t-shirt is knit from heavier, denser jersey than a standard tee. The weight is given in grams per square metre, gsm. There is no fixed industry cut-off for the word, so the number tells you more than the label.
What gsm means
Gsm is the weight of one square metre of the fabric, in grams. More grams in the same area means more cotton: a thicker, more opaque jersey. Gsm describes the fabric, not the finished shirt, so two shirts of the same gsm can still differ in cut, yarn and collar.
How to measure it at home
- Mark a square of 10 × 10 cm on the fabric, or use a swatch of that size.
- Weigh it on a kitchen or jewellery scale that reads to 0.1 g.
- Multiply the grams by 100. That is the gsm.
Example: a square that weighs 2.4 g is 240 gsm. On a finished shirt, a fabric gauge or the maker’s specification gives the same figure without cutting anything.
Grams and ounces
Many US listings give fabric weight in ounces per square yard. Divide gsm by 33.906 to convert. The table runs the arithmetic for common weights.
| Grams per square metre | Ounces per square yard |
|---|---|
| 140 gsm | 4.1 oz/yd² |
| 160 gsm | 4.7 oz/yd² |
| 180 gsm | 5.3 oz/yd² |
| 200 gsm | 5.9 oz/yd² |
| 220 gsm | 6.5 oz/yd² |
| 240 gsm | 7.1 oz/yd² |
| 260 gsm | 7.7 oz/yd² |
| 280 gsm | 8.3 oz/yd² |
| 300 gsm | 8.8 oz/yd² |
Where 240 gsm sits
240 gsm is a heavy weight for a t-shirt. Heavier jersey generally drapes less than light jersey, which is why it suits a boxy cut that stands away from the body. It is also warmer: on very hot days, a lighter fabric breathes more, and jerseys of 300 gsm and more lean toward cold weather.
The weight is one line of a specification. Collar, yarn, seams and fit decide the rest, and they are worth reading in the same detail.