🧵 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.
Final check. Divide by 33.9057, so 100 GSM is 2.95 oz/yd² and 400 GSM is 11.8. An answer larger than the GSM figure means the division was replaced by a multiplication.
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.