A fabric listing tells you five things that matter: fiber content, construction (woven or knit, and which weave), weight, width, and behavior (drape, stretch, opacity). Weight is usually given in GSM, grams per square meter; multiply GSM by 0.0295 to get ounces per square yard. Below about 100 GSM (3 oz/yd²) is light and suits blouses and linings, 100–200 GSM (3–6 oz/yd²) covers most shirts, dresses and skirts, and above 250 GSM (7.4 oz/yd²) is for trousers, jackets, sweatshirts and bags.
What does GSM mean, and how does it convert to ounces?
GSM is the weight of one square meter of fabric in grams. It measures density, not thickness: a 120 GSM double gauze feels thicker than a 120 GSM poplin because its two layers trap air.
| GSM | oz/yd² | Weight class | Typical fabrics and uses |
|---|---|---|---|
| Under 100 | Under 3 | Very light | Voile, lawn, chiffon: blouses, linings, summer tops |
| 100–170 | 3–5 | Light | Poplin, quilting cotton, challis, shirting: shirts, dresses, skirts |
| 170–270 | 5–8 | Medium | Linen, twill, jersey, chambray: trousers, skirts, T-shirts |
| 270–400 | 8–12 | Medium-heavy | Denim, canvas, French terry: jackets, bags, sweatshirts |
| Over 400 | Over 12 | Heavy | Heavy canvas, upholstery, coating: bags, coats, home pieces |
The conversion: 1 oz/yd² is about 33.9 GSM. So 150 GSM is about 4.4 oz/yd², and a 10 oz denim is about 340 GSM.
Note: Some shops, especially in the US and for knits and fleece, quote ounces per linear yard: the weight of a 1 yd length at the fabric's full width. For a 60 in wide fabric, that figure is about 1.67 times the oz/yd² figure. A "10 oz" fleece sold that way weighs only about 6 oz/yd², or 200 GSM. If a listing seems heavy for its type, check which unit it uses.
How do you read fiber content?
Fiber content is listed by percentage. "95% cotton, 5% elastane" is a stretch jersey; "55% linen, 45% cotton" is a blend that frays less than pure linen. A few names to know:
- Viscose, rayon, modal, lyocell: cellulose fibers made from wood pulp, all with lovely drape. TENCEL is a brand name for lyocell and modal.
- Elastane, spandex, Lycra: the same stretchy fiber under different names. 2–5% is enough to change how a fabric behaves.
- Polyester, nylon (polyamide), acrylic: synthetics, durable and wrinkle-resistant, less breathable.
- Linen and flax: the same fiber. Hemp and ramie are similar bast fibers, strong and crisp.
Is it woven or knit, and what do the weave names mean?
The construction tells you as much about behavior as the fiber does. If the basics are new to you, read woven vs knit fabric first.
| Term | What it is | Typical weight |
|---|---|---|
| Lawn | Fine, smooth plain weave, slightly crisp | 60–100 GSM |
| Voile | Sheer, soft plain weave | 50–90 GSM |
| Poplin | Tight plain weave with a fine rib, crisp | 100–140 GSM |
| Chambray | Plain weave with a colored warp and a white weft | 120–170 GSM |
| Twill, drill | Diagonal weave lines, strong | 180–300 GSM |
| Sateen | Cotton in a satin weave, with a soft sheen | 120–200 GSM |
| Canvas, duck | Heavy plain weave | 280–500 GSM |
| Double gauze | Two layers of gauze tacked together | 110–150 GSM |
| Challis | Soft, fluid plain weave, often viscose | 100–130 GSM |
| Single jersey | Knit with a smooth front and loops on the back; curls | 140–200 GSM |
| Interlock | Double knit, smooth on both sides, does not curl | 180–250 GSM |
| Ponte | Firm double knit that holds its shape | 280–350 GSM |
| French terry | Knit with soft loops on the back | 240–350 GSM |
What does "drape" mean in a fabric listing?
Drape is how a fabric hangs and folds under its own weight. "Fluid" or "drapey" fabrics (viscose crepe, silk charmeuse, bamboo jersey) fall close to the body in soft folds; "crisp" or "structured" fabrics (poplin, taffeta, canvas) stand away from it.
Drape and weight are separate qualities. A 120 GSM viscose crepe and a 120 GSM cotton poplin weigh the same and behave completely differently. Match the drape to the pattern: a gathered skirt in a crisp fabric stands out like a bell, while the same skirt in a fluid fabric falls straight down.
How do you read stretch in a listing?
Look for three pieces of information:
- Direction. "Two-way stretch" usually means the fabric stretches in one direction, normally across the width; "four-way stretch" means it stretches both across and along the length. Sellers do not all use the terms the same way, so look for the percentage too.
- Amount. The stretch percentage is how far 10 cm stretches comfortably: 50% means 10 cm reaches 15 cm. Knit patterns state a minimum, and the fabric must meet it.
- Recovery. Good recovery means the fabric springs back after stretching. Elastane improves it; fabrics without it can bag over time.
Wovens can stretch slightly too, either from elastane (stretch denim, stretch sateen) or from a crepe or loose weave, which sellers call mechanical stretch.
Why does fabric width matter?
Fabric is commonly sold about 110 cm (45 in), 140 cm (55 in) or 150 cm (60 in) wide, and the width changes how much length you need. Check whether the quoted width includes the selvedges; the usable width can be a few centimeters less. Every Sewly pattern gives quantities for those three widths, and the fabric yardage calculator handles any other width.
What other words should you watch for?
- Nap or pile: velvet, corduroy and brushed fabrics look different depending on direction, so every piece must face the same way, which takes more fabric.
- Directional print: a print with a clear up and down, with the same consequence.
- Repeat: the length after which a print repeats; matching it across seams needs extra fabric.
- Opacity: "semi-sheer" means you may need a lining or an underlayer.
- Sanforized or pre-shrunk: treated to shrink less, though most fabrics still shrink a little.
- Deadstock or mill end: surplus fabric, often good quality and limited in length.
When a listing leaves you guessing, order a swatch. A few minutes with the fabric in your hands answers more questions than any description.