Every fabric can be described by a short list of numbers and terms: what it is made of, how much it weighs, and how its yarns are held together. Once you can read those three things — composition, GSM, and construction — you can predict how almost any material will feel, drape, wear, and wash before you ever touch it.
That is the whole idea behind this guide. No trend talk, no brand talk: just the specs, what they mean, and how to use them. One caveat applies throughout — the figures below are typical ranges, not guarantees. Real fabrics vary by mill, lot, and finish, so always verify the actual spec sheet before you buy or commit a production run.
The three specs that describe any fabric
A useful fabric description answers three questions:
- What is it made of? — the fibre composition (e.g. 100% cotton, or 95% cotton / 5% elastane).
- How heavy is it? — the weight, usually in GSM (grams per square metre).
- How is it built? — the construction: woven, knitted, or nonwoven, and which specific weave or knit.
A spec sheet will add more — width, shrinkage, finish, care — but these three carry most of the predictive power. "200 GSM 100% cotton single jersey" tells an experienced buyer nearly everything: a mid-weight T-shirt fabric, soft, stretchy across the width, breathable, prone to some shrinkage unless pre-shrunk.
GSM: what fabric weight actually tells you
GSM means grams per square metre — take one square metre of the fabric and weigh it. (You will also see oz/yd², common for denim; roughly, 1 oz/yd² is about 34 GSM.) GSM is the fastest single clue to how a fabric behaves:
- Lightweight (roughly under 150 GSM). Voile, lawn, chiffon, lightweight jerseys. Airy, drapey, often semi-sheer. Summer shirts, linings, flowy dresses.
- Mid-weight (roughly 150–300 GSM). Most T-shirt jerseys, poplins, chambrays, lighter twills. The everyday-apparel zone: structured enough to hold shape, light enough to wear comfortably.
- Heavyweight (roughly 300 GSM and up). Denim, canvas, French terry and fleece for sweats, upholstery cloth. Durable, warm, structured — and slower to dry.
Two warnings. First, these bands are conventions, not standards — one mill's "midweight" is another's "heavy," which is exactly why you read the number instead of the label. Second, GSM is not a quality score. A high GSM means more material per square metre, not better material. A beautifully spun 130 GSM shirting can outlast a coarse 220 GSM jersey. Weight tells you what a fabric is for, not how good it is.
Composition: fibres set the rules
The fibre content sets the fabric's non-negotiables — how it handles moisture, heat, stretch, and time. In one line each:
- Cotton — soft, breathable, absorbs moisture readily; wrinkles, and can shrink unless the fabric was pre-shrunk or the label says otherwise.
- Linen — very breathable and strong, with a crisp, dry hand; wrinkles as a personality trait.
- Wool — insulating even in damp conditions, naturally elastic and odour-resistant; most wools can felt and shrink in hot, agitated washing.
- Silk — lightweight, lustrous, strong for its weight; sensitive to sunlight, sweat, and rough washing.
- Polyester — durable, quick-drying, holds its shape and resists wrinkles; less absorbent, so it can feel clammy and hold onto odours.
- Nylon — exceptionally strong and abrasion-resistant with a smooth hand; common in outerwear, activewear, and bags.
- Elastane (spandex/Lycra) — never the main fibre, but even 2–5% in a blend adds stretch and, crucially, recovery — the fabric snaps back instead of bagging out.
- Viscose/rayon and its relatives (modal, lyocell) — plant-derived, chemically processed fibres with a soft hand and fluid drape; many weaken when wet, so care matters.
Blends are compromises on purpose. A 65/35 polyester/cotton shirt trades some of cotton's breathability for polyester's wrinkle resistance and durability. A 95/5 cotton/elastane jersey keeps a cotton hand and adds recovery. When you read a blend, ask what each fibre was hired to do — and remember the percentages on a label describe that fabric's stated recipe, not a family guarantee. Verify the spec sheet.
Construction: woven vs knit (and why it matters more than people think)
Two fabrics with identical composition and GSM can behave completely differently depending on how they are built.
Wovens
Woven fabric is made on a loom from two yarn sets crossing at right angles: warp (lengthwise) and weft (crosswise). Wovens are stable, crisp, and — unless elastane is added — have very little stretch. The three foundational weaves:
- Plain weave — over one, under one. Simple, stable, matte. Poplin, lawn, voile, muslin, many shirtings.
- Twill — the yarn steps over two or more, creating a diagonal rib. Denser, drapier, hides soil, resists wrinkles better than plain weave. Denim, chino, gabardine.
- Satin — long floats on the surface produce lustre and slipperiness, at the cost of snag resistance. Eveningwear, linings. (Satin is a weave; the fibre can be silk or polyester.)
Knits
Knit fabric is made from interlooping yarns — one continuous yarn (or set) looped through itself. Loops move, so knits stretch even with zero elastane. Common knits:
- Single jersey — the classic T-shirt fabric; smooth face, looped back, stretchy, edges curl when cut.
- Rib — vertical ridges with strong crosswise stretch and recovery; cuffs, collars, fitted tops.
- Interlock — a double-knit; both faces smooth, more stable and opaque than single jersey at the same weight.
- French terry and fleece — looped or brushed backs that trap air; sweatshirt territory.
The practical rule: wovens hold a shape; knits follow one. Structured items (dress shirts, trousers, bags, upholstery) usually want wovens; anything that must move and stretch with a body (tees, activewear, baby clothes) usually wants knits.
Reading a real spec sheet
A typical fabric spec sheet lists composition, weight (GSM or oz/yd²), width (commonly ~140–160 cm for many apparel fabrics, but it varies), construction, finish (e.g. mercerised, brushed, peached), shrinkage (often quoted as a maximum percentage after a standard wash test), and care guidance. Read it in this order:
- Composition — does the fibre suit the job and the care routine?
- GSM — is the weight right for the garment or product?
- Construction — woven or knit, and which one?
- Width — it changes how much yardage you need and what a "per metre" price really costs you.
- Shrinkage and finish — the difference between a garment that fits after five washes and one that does not.
If a listing gives you only a fibre name and a photo, treat every property as unverified. Ask for the sheet, or order a swatch and weigh it — a kitchen scale and a cut square get you a usable GSM estimate. For structured, spec-first entries on individual fabrics, the reference pages on Dexitex document each material in exactly this format.
Once you can read the specs, the next skill is applying them to a project — matching weight, fibre, and construction to what you are actually making, which is covered in our guide to choosing fabric — and keeping the fabric to spec at home, covered in the fabric care guide.
FAQ
What is a good GSM for a T-shirt?
Most T-shirt single jerseys fall somewhere around 140–200 GSM: lighter feels airier and drapes closer to the body, heavier feels more substantial and opaque. Premium "heavyweight" tees often sit above 220 GSM. None of these numbers is a quality guarantee — check the actual spec and, ideally, a swatch.
Is higher GSM always better quality?
No. GSM measures mass per area, not fibre quality, yarn quality, or construction quality. A finely spun lightweight fabric can outperform a heavy coarse one. Use GSM to judge suitability for a purpose; judge quality by fibre grade, spinning, construction, and finish — verified on the spec sheet.
How can I tell a woven from a knit?
Stretch it and look closely. A knit shows rows of interlocking loops and stretches noticeably (especially across the width) even without elastane; a woven shows a criss-cross grid of yarns and barely stretches along its straight grains. Cut edges also behave differently: many single knits curl, while wovens fray.
Does fabric composition on the label always match reality?
Labels are regulated in most markets and are usually accurate within stated tolerances, but errors and loose supply-chain paperwork happen. For purchases where composition genuinely matters — production runs, allergies, performance requirements — rely on the supplier's spec sheet and, for large orders, independent lab verification rather than the hangtag alone.
Ready to go deeper than the label? Every fabric on Dexitex is documented by exactly these specs — composition, GSM, construction, properties, uses, and care — in one structured entry. Start with the fabric reference library on Dexitex and read any material like a professional.
