GSM to oz Converter
Most of the world quotes fabric weight in GSM (grams per square meter); mills and brands in the United States quote it in oz/yd² (ounces per square yard). Type a number in either box and the other one updates.
The formula
- oz/yd² = GSM ÷ 33.9057 — 180 GSM ÷ 33.9057 = 5.31 oz/yd².
- GSM = oz/yd² × 33.9057 — 8 oz/yd² × 33.9057 = 271 GSM.
The factor comes from the units themselves: one ounce is 28.349523125 grams and one square yard is 0.83612736 square meters, so one ounce per square yard is 28.349523125 ÷ 0.83612736 = 33.9057 grams per square meter.
Common fabric weights
| GSM (g/m²) | oz/yd² | Typical use |
|---|---|---|
| 100 | 2.95 | Sheer and very light knits |
| 120 | 3.54 | Light summer jersey |
| 140 | 4.13 | Lightweight t-shirt jersey |
| 160 | 4.72 | Light t-shirt jersey |
| 180 | 5.31 | Standard t-shirt jersey |
| 200 | 5.90 | Midweight t-shirt jersey |
| 220 | 6.49 | Heavyweight t-shirt jersey |
| 240 | 7.08 | Heavy tee, light French terry |
| 260 | 7.67 | French terry shorts and light sweatpants |
| 280 | 8.26 | Light hoodie and jogger fleece |
| 300 | 8.85 | Midweight sweatshirt fleece |
| 320 | 9.44 | Standard hoodie fleece |
| 350 | 10.32 | Heavy hoodie fleece |
| 400 | 11.80 | Very heavy fleece for structured hoodies |
Which unit should your spec use?
Put the weight in your bill of materials next to the shell fabric, in the unit your supplier works in: GSM for mills in China, India, Turkey and most of Europe, oz/yd² for US mills and for anything sold as "5.3 oz jersey" or "8 oz fleece". If you are unsure, give both — the tech pack generator has a place for it in the BOM, and it keeps the number in the document your factory signs off on.
Measuring a swatch by hand instead? Calculate the GSM first, then come back here if you need ounces.
FAQ
In fabric, is "oz" the same as oz/yd²?
Yes. When a fleece is described as 8 oz, it means 8 ounces per square yard. It is not ounces per square meter or per square inch.
What is 180 GSM in oz?
180 GSM is 5.31 oz/yd², the classic midweight t-shirt jersey. For reference, 150 GSM is 4.42 oz and 240 GSM is 7.08 oz.
What is 8 oz fleece in GSM?
About 271 GSM. Fleece is often sold in whole ounces in the US: 6 oz is about 203 GSM, 8 oz about 271 GSM and 10 oz about 339 GSM.
Why is the conversion factor 33.9057?
One ounce is 28.349523125 grams, or 28.3495 g rounded, and one square yard is 0.83612736 square meters, or 0.8361 m² rounded. Divide one by the other and you get 33.9057 grams per square meter per ounce per square yard.
Is GSM the same as g/m²?
Yes, they are the same unit. Some mills write g/m² or gsm, which is short for grams per square meter.
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