GSM to oz/yd² fabric weight converter
Compare fabric listings from anywhere: grams per square metre, ounces per square yard and the per-linear-yard figures some shops quote, with the weight class and what your cut will weigh.
GSM, oz/yd² and the linear yard
GSM is the mass of one square metre of fabric in grams. oz/yd² is the same idea in ounces per square yard, used for denim, canvas and many US listings. Both describe the cloth itself, so they do not change with width. The exact link is 1 oz/yd² = 33.906 g/m², because an ounce is 28.349523125 g and a square yard is 0.83612736 m².
Some shops, mostly in the US trade, quote ounces per linear yard instead: what one yard cut from the bolt weighs at its full width. That figure grows with width, so enter the width too. A 6 oz/yd² cloth at 60 in wide weighs 10 oz per linear yard (6 × 60 ÷ 36). The metric version is grams per linear metre: 200 gsm at 150 cm wide is 300 g per metre.
Using the converter
Type the weight, choose how the listing gives it, and check the width. You get all four figures, the weight class and what your length weighs, handy for postage or for comparing two shops. No listing? Cut a swatch and weigh it in step 2. A 100 cm² circle cutter makes it simple: grams × 100 = GSM. Use a big swatch on a kitchen scale; its 1 g steps are too coarse for a small square, and the converter shows how far off the reading could be.
Weight is only one clue. Weave, fibre and finish change drape: a 200 gsm linen and a 200 gsm jersey behave very differently. The classes below are rough guides, not grades.
Fabric weight classes
| Class | GSM | oz/yd² | Typical fabrics |
|---|---|---|---|
| Sheer to very light | under 100 | under 2.9 | chiffon, georgette, organza, voile, batiste |
| Light | 100–170 | 2.9–5 | lawn, poplin, quilting cotton, chambray, viscose challis |
| Medium | 170–270 | 5–8 | linen, cotton jersey, flannel, needlecord, lighter twills |
| Heavy | 270–400 | 8–11.8 | denim, canvas, corduroy, sweatshirt fleece, many coatings |
| Very heavy | 400 and up | 11.8 and up | heavy canvas and duck, upholstery fabric, thick coatings, faux fur |
These bands are our own rule of thumb. There is no official scale, and shops draw the lines in different places: compare the two guides in the sources, which disagree with each other by a class or so. Use GSM itself when you compare two fabrics.
Sources
- NIST, Guide to the SI, Appendix B.9: ounce (avoirdupois) per square yard = 3.390 575 × 10⁻² kg/m², from the exact ounce and yard.
- ASTM International, D3776/D3776M, Standard Test Methods for Mass Per Unit Area (Weight) of Fabric: fabric weight as mass per unit area or per unit length, measured without selvedges.
- Sew Me Sunshine, Guide to fabric weight, and Linda's Electric Quilters, Fabric weight guide: two published sets of weight classes, for comparison with ours.
Questions
How do I convert GSM to oz/yd²?
Divide the GSM by 33.906. For example, 200 GSM is 5.9 oz/yd², and 340 GSM is about 10 oz/yd². To go the other way, multiply ounces per square yard by 33.906: 12 oz/yd² denim is about 407 GSM.
What is the difference between oz/yd² and oz per linear yard?
Ounces per square yard describe the cloth itself. Ounces per linear yard describe one yard cut off the bolt at its full width, so the same cloth reads heavier when it is wider. Always check which one a listing means before comparing two fabrics.
Is 200 GSM fabric heavy?
It sits in the middle. By our bands 200 GSM (about 5.9 oz/yd²) is a medium weight, typical of linen, cotton jersey and flannel. It is heavy for a blouse and light for jeans or a bag.
How can I measure GSM at home?
Cut a piece of known size, weigh it and divide the grams by the area in square metres. A 10 × 10 cm square or a 100 cm² circle needs a scale that reads to 0.01 g; with a kitchen scale, weigh a much larger piece or several layers so the 1 g steps matter less.