A fabric spec sheet is a supplier's written promise about what the cloth is. Read it in order — composition, weight, construction, width, then the performance and care lines — and you can predict most of how a fabric will behave before a single metre ships. Skip it and you find out after cutting.
The checklist below is the order a sourcing person actually works in, whether they are buying 20 metres for a sample run or 2,000 for production. Every figure on a spec sheet is a nominal value with a tolerance behind it, so treat all of them as claims to verify against a physical sample, not as guarantees.
The ten-line checklist
Before you commit, confirm you can answer all ten:
- Composition — every fibre, with percentages that total 100%.
- Weight — GSM or oz/yd², and whether it's greige or finished weight.
- Construction — woven or knitted, and which structure.
- Width — and whether it's cuttable/usable width or edge-to-edge.
- Shrinkage — residual shrinkage after washing, warp and weft.
- Colourfastness — to washing, rubbing (crocking), light, perspiration.
- Durability — abrasion and pilling results, with the test method named.
- Finish — mercerised, brushed, enzyme washed, coated, water repellent.
- Certifications — what is certified, by whom, and covering what scope.
- Commercial terms — MOQ, lead time, roll length, price basis, tolerances.
Anything missing is a question for the supplier, not an assumption for you.
Composition: the line that sets every limit
Composition is the fibre content, written as percentages. It governs how the fabric absorbs moisture, how it takes dye, how it responds to heat, and how it ages. Get this line wrong and no other spec saves you.
Read it precisely. "Cotton rich" is marketing; 60% cotton / 40% polyester is a spec. Blends behave like a negotiated compromise between their parts — adding polyester to cotton typically improves wrinkle recovery, dimensional stability and drying speed while reducing breathability and comfort in heat. A few percent of elastane adds stretch and recovery but constrains ironing temperature and shortens practical service life, because elastane degrades with heat, chlorine and UV over time.
Two habits worth building: check the percentages add to 100, and check whether the sheet distinguishes the face yarn from any backing or coating. A "100% cotton" canvas with a polyurethane back coating is not 100% cotton in any way that matters to care or recycling.
Weight: what GSM does and doesn't tell you
Weight is usually quoted in GSM (grams per square metre) or oz/yd² (ounces per square yard). It tells you how much yarn is packed into an area, which correlates with opacity, warmth, drape and hand — but not with quality.
Three things to confirm:
- Finished, not greige. Finishing (singeing, mercerising, brushing, compacting) changes weight. A sheet quoting loom-state weight will read light against what you receive.
- The tolerance. Weight is generally quoted with a permitted variance; ask what it is and whether it's per roll or per lot.
- The unit. Roughly 1 oz/yd² is about 34 GSM, so a "7 oz" fabric is near 240 GSM. Mixing the two units is a classic ordering error.
If you want to check a claim yourself, weighing a cut swatch takes two minutes — the method is in our guide to calculating GSM, and the wider vocabulary of specs sits in the fabric specs explainer.
Construction: woven or knitted, and which structure
Construction determines stretch, fray behaviour, recovery and how the fabric takes a seam. A spec sheet should name the structure, not just the family.
- Wovens — plain, twill, satin, oxford, canvas. Look for the weave name plus yarn counts and thread density (ends and picks per unit length). Wovens have little stretch on the straight grain and considerable give on the bias.
- Knits — single jersey, interlock, rib, French terry, piqué. Look for the knit type plus gauge (needles per inch). Knits stretch, and their recovery depends on structure and elastane content, not weight.
Same fibre, same GSM, different construction: entirely different garment. An interlock is more stable and more opaque than a single jersey at the same weight, because it is a double knit.
Width: ask which width is being quoted
Width is quoted in centimetres or inches, and the number you care about is cuttable (usable) width — the width excluding selvedges and any edge distortion. Tubular knits may be quoted as tube width or open width, which differ by a factor of two in practice.
Width drives yield. A fabric that is cheaper per metre but narrower can cost more per finished garment once the marker is laid, so always convert price to a per-unit-of-output basis before comparing quotes.
Shrinkage, colourfastness, and abrasion
These are the performance lines, and they are where "verify the spec sheet" turns into "verify the sample."
Shrinkage is reported as residual dimensional change after washing, usually as a percentage in the warp/length and weft/width directions, and often to a named test standard. Note whether it is quoted for washing, tumble drying, or both — tumble drying almost always costs more. Cottons and cellulosics move more than polyester; knits move more than stable wovens.
Colourfastness is graded, typically on a 1–5 scale, for separate hazards: washing, rubbing (dry and wet crocking), light, and perspiration. A fabric can be excellent to washing and poor to crocking, which is why deep-dyed denim marks pale upholstery. Read every sub-rating, not the headline.
Abrasion and pilling results are only meaningful with the method named. Abrasion is commonly reported as Martindale cycles or Wyzenbeek double rubs; pilling as a graded rating after a set number of cycles. Numbers from different methods are not interchangeable — never compare a Martindale figure to a Wyzenbeek one. What happens after purchase matters just as much, which is where the fabric care guide picks up.
Finish and certifications
Finish explains behaviour the fibre alone doesn't. Mercerising adds lustre and dye uptake to cotton; brushing raises a soft nap and can increase pilling; enzyme or stone washing softens and pre-relaxes; coatings and durable water repellent treatments add function but change hand, breathability and recyclability — and many wear off with washing. Ask how many wash cycles a functional finish is rated for.
Certifications should be read for scope, not vibes. OEKO-TEX STANDARD 100 certifies that a tested article meets limits for specified harmful substances — it is a chemical safety scheme, not an environmental or social one. GOTS covers organic fibre content plus processing and social criteria along the chain. GRS covers recycled content and chain of custody. None of them make a fabric "sustainable" on its own, and a certificate belongs to a specific article and validity period — ask for the certificate number and check it.
Before you order: verify on cloth, not paper
- Request a hanger or swatch and handle it: drape, hand, opacity against light, stretch and recovery.
- Order a lab dip if colour matters, and approve it under the light condition your product will be seen in.
- Wash-test a sample on your intended care cycle and measure shrinkage yourself between marked points.
- Confirm lot behaviour: ask whether the order ships from one dye lot, and what the shade tolerance is between lots.
- Nail the commercial lines: MOQ, roll length, lead time, quantity tolerance, and what happens if the delivered goods miss spec.
FAQ
What is a fabric spec sheet?
A fabric spec sheet (or technical data sheet) is the supplier's structured description of a fabric: composition, weight, construction, width, and its performance and care results. It is the document you compare quotes against and the reference you hold a delivery to.
What should I check first on a fabric spec sheet?
Composition, then weight, then construction. Those three set the ceiling on how the fabric can behave. Width and the performance lines refine the decision, but if the fibre content or the construction is wrong for the job, nothing else rescues it.
Is GSM the most important number on a spec sheet?
No. GSM tells you mass per area, which predicts opacity, warmth and hand — not quality or durability. A finer yarn at a lower GSM can outperform a coarse heavy one. Read GSM alongside fibre, yarn spec and construction.
How much shrinkage is acceptable in a fabric?
There is no universal figure — it depends on fibre, construction, finish and the care cycle you intend. What matters is that a residual shrinkage figure is stated with its test method, and that you verify it by washing a marked sample yourself before committing.
Do certifications like OEKO-TEX mean a fabric is sustainable?
No. OEKO-TEX STANDARD 100 is a chemical-safety scheme for tested articles; GOTS adds organic content and processing criteria; GRS addresses recycled content and chain of custody. Each covers a defined scope for a specific certified article — read the scope and verify the certificate rather than reading the logo as a general environmental claim.
Want the specs before the spec sheet arrives? Every material on Dexitex is documented the same way a technical data sheet is — composition, weight, construction, properties, and care — so you can compare candidates before you ask a supplier for anything. Start with the fabric reference library on Dexitex and shortlist on specs, not adjectives.
