🧵 Textile
GSM to oz Converter
Enter grams per square metre and press Convert to get ounces per square yard. 1 oz/yd² is 33.91 g/m², so 180 GSM is 5.31 oz.
About the GSM to oz Converter
Fabric weight is quoted in GSM (grams per square metre) almost everywhere except the US, where oz/yd² is standard for apparel, and the conversion is not a simple linear one because both mass and area change. The exact factor is 28.349523125 ÷ 0.83612736 = 33.9057 g/m² per oz/yd².
The number tells you what the cloth is for: 120–150 GSM is a light T-shirt, 180–220 GSM a standard tee, 280–340 GSM a hoodie, and 10–14 oz denim is 339–475 GSM.
How the calculation works
- oz/yd² = GSM ÷ 33.9057
- GSM = oz/yd² × 33.9057
- 1 oz = 28.349523125 g · 1 yd² = 0.83612736 m²
Reference values
| GSM (g/m²) | oz/yd² | Typical fabric |
|---|---|---|
| 120 GSM | 3.54 oz | Light voile, summer shirt |
| 150 GSM | 4.42 oz | Light T-shirt |
| 180 GSM | 5.31 oz | Standard T-shirt |
| 220 GSM | 6.49 oz | Heavy T-shirt |
| 280 GSM | 8.26 oz | French terry, hoodie |
| 340 GSM | 10.03 oz | Heavy hoodie |
| 475 GSM | 14.01 oz | 14 oz denim |
| 610 GSM | 17.99 oz | Canvas, workwear |
Worked examples
- 160 GSM is 4.72 oz/yd², a light summer jersey.
- 300 GSM is 8.85 oz, a mid-weight hoodie fabric.
- 407 GSM is 12.0 oz, the classic 12 oz denim weight.
Why the factor is 33.9
An ounce is 28.3495 g and a square yard is 0.836127 m², so one ounce per square yard is 28.3495 ÷ 0.836127 = 33.9057 g/m². Both mass and area change, which is why you cannot use 28.35 alone — that would overstate the weight by 18%.
Common mistakes
- Dividing by 28.35 instead of 33.91, mixing a mass conversion with an area conversion.
- Comparing GSM of a knit with oz of a woven without accounting for shrinkage and finish.
- Assuming a heavier fabric is always stronger. Yarn quality and weave matter more than weight alone.
A last check on the numbers: 37 Grams per square metre works out to 1.091 Ounces per square yard, and reversing that with the same factor brings you back to 37 Grams per square metre. Because Grams per square metre to Ounces per square yard is a single multiplication, any tool that gives a different figure for the same input is rounding somewhere in the middle rather than only at the end.
Frequently asked questions
GSM to ounces per square yard chart
One ounce per square yard is 33.9057 grams per square metre, so the conversion is a single division. The chart covers the range from lightweight shirting to heavy canvas.
| Grams per m2 | Ounces per yd2 | Grams per yd2 |
|---|---|---|
| 80 gsm | 2.36 oz/yd2 | 66.9 g/yd2 |
| 100 gsm | 2.95 oz/yd2 | 83.6 g/yd2 |
| 120 gsm | 3.54 oz/yd2 | 100.3 g/yd2 |
| 140 gsm | 4.13 oz/yd2 | 117.1 g/yd2 |
| 160 gsm | 4.72 oz/yd2 | 133.8 g/yd2 |
| 180 gsm | 5.31 oz/yd2 | 150.5 g/yd2 |
| 200 gsm | 5.90 oz/yd2 | 167.2 g/yd2 |
| 220 gsm | 6.49 oz/yd2 | 183.9 g/yd2 |
| 240 gsm | 7.08 oz/yd2 | 200.7 g/yd2 |
| 260 gsm | 7.67 oz/yd2 | 217.4 g/yd2 |
| 280 gsm | 8.26 oz/yd2 | 234.1 g/yd2 |
| 300 gsm | 8.85 oz/yd2 | 250.8 g/yd2 |
| 320 gsm | 9.44 oz/yd2 | 267.6 g/yd2 |
| 340 gsm | 10.03 oz/yd2 | 284.3 g/yd2 |
| 360 gsm | 10.62 oz/yd2 | 301.0 g/yd2 |
| 380 gsm | 11.21 oz/yd2 | 317.7 g/yd2 |
| 400 gsm | 11.80 oz/yd2 | 334.5 g/yd2 |
As a rough guide, 100-150 gsm is shirt weight, 150-220 gsm is a standard T-shirt or dress, 250-350 gsm is sweatshirting, and above 400 gsm is canvas or upholstery. Denim is usually quoted in ounces per square yard directly, which is why a 12 oz jean and a 400 gsm fabric are the same cloth described two ways.