Custom Fabric Development: A Complete Guide to Knits, Wovens, GSM, and Yarn Counts

Fabric is 50-65% of your per-piece cost and the single hardest spec to get right, yet most first-time buyers describe it in two words: “soft cotton” and hope for the best. This guide covers the fabric decisions that actually determine your garment quality and cost — knit vs woven, GSM, yarn count, construction type, and the three tests to run before you commit to bulk.

Why fabric is where OEM orders fail

• Fabric is the largest cost line and the least understood by first-time buyers
• “Soft cotton” means nothing: 100% cotton can range from 90 gsm to 320 gsm, and jersey can be single or double knit
• Fabric choice constrains everything downstream: decoration method, shrink behavior, drape, durability, MOQ
• Fabric substitution is the #1 cause of sample-to-bulk quality divergence

Knit vs woven: the first decision

Knit

• Made from interlocking loops of yarn (one continuous thread forming rows of “V” shapes)
• Stretches naturally, no side seams needed (cut-and-sew construction)
• Casual, comfortable, wrinkle-resistant, takes print and embroidery well
• Main products: t-shirts, hoodies, joggers, sweaters, base layers, sportswear
• Lower MOQ, faster sampling, easier to prototype

Woven

• Made from two sets of yarn woven perpendicular to each other (warp and weft)
• Does not stretch (unless elastane is added), drapes more structurally
• Formal, durable, holds shape, higher abrasion resistance
• Main products: dress shirts, chinos, jackets, trousers, workwear
• Higher MOQ, more complex sampling, more expensive fabric mills

How to decide

GSM: the number that matters most

GSM (grams per square meter) is the single most important fabric spec. It determines opacity, drape, hand feel, durability, and cost. Getting GSM wrong is the #1 reason a fabric feels cheap.

GSM ranges by product

Common GSM mistakes

• Going too light to save cost: saving 0.30 USD/piece on fabric often causes returns, reviews, and brand damage worth 10x that
• Copying a competitor’s GSM without testing: their fabric may be a different construction with the same GSM
• Confusing GSM with weight per garment: 180 gsm single jersey uses roughly 200-220 g of fabric per adult t-shirt, but a hoodie at 320 gsm fleece uses 600-800 g
• Not specifying GSM in the tech pack: factory defaults to whatever is cheapest

Yarn count: the spec most buyers skip

Yarn count describes yarn thickness. For a comparable “feel,” yarn count matters as much as GSM.

Common yarn counts for cotton

Note: higher yarn count = finer yarn = softer, more expensive. So 40s is softer and pricier than 24s.

Combed vs carded vs ring-spun

• Carded: cheapest, retains some fiber impurities, slightly scratchy. 20-30% cheaper than combed.
• Combed: removes short fibers, smoother and more durable. The standard for quality basics.
• Ring-spun: twisted and thinned during spinning, strongest and softest. 15-25% more expensive than combed. Used for premium tees.

Polyester yarn counts

• Polyester uses denier (D) instead of count (S): 75D, 100D, 150D, 300D
• 75D-100D: fine, smooth, cool to the touch (good for poly shirts, lining)
• 150D: medium weight, standard for performance wear
• 300D: heavy, durable, structured (good for bags, outerwear lining, sublimation blanks)

Knit constructions you should know

Single jersey

• The most common t-shirt construction
• Light on one side, slightly different texture on the other (face vs. back)
• Stretches 4-way, drapes fluidly, ideal for screen print and DTG
• 130-260 gsm typical range

Pique (polo knit)

• Textured, waffle-like surface with small holes
• More breathable, more structured, holds collar shape
• The standard polo shirt construction
• 180-240 gsm typical

French terry

• Loopback construction: flat face with soft loops on the inside
• The classic sweatshirt and hoodie body fabric
• 280-400 gsm typical
• Not to be confused with fleece (terry is unbrushed, fleece is brushed)

Fleece (brushed back)

• French terry or loopback that has been brushed on the inside for softness
• Warmer than terry, softer hand feel, more “premium”
• 280-450 gsm typical

Interlock

• Two layers of single jersey knitted together
• Doesn’t curl, doesn’t roll, smooth surface
• Better for printing than single jersey (no curl at the hem)
• 220-280 gsm typical

Rib knit

• Vertical ribs, stretches a lot
• Used for collars, cuffs, waistbands, tank tops
• 2×2, 3×3, or 1×1 rib constructions
• Usually 1 cm wider than the body fabric for stretch recovery

Terry (bath terry)

• Very high loop pile, absorbent
• Towels, bathrobes, some sweatshirts
• Not typically used for apparel tees

Mesh

• Open structure with visible holes
• Sports jerseys, performance panels, athletic underlayers
• 140-220 gsm typical

Scuba / neoprene

• Thick, structured, bonded double-layer knit
• Modern structured garments, skirts, jackets
• 280-400 gsm

Woven constructions you should know

Plain weave

• Simplest: each warp yarn alternates over-under each weft yarn
• Versatile, balanced, moderate durability
• Used for dress shirts, light trousers

Twill

• Diagonal rib pattern (2/1 or 3/1 warp over weft)
• More durable than plain weave, drapes better, shows less wrinkling
• The classic chino / denim / workwear construction
• 2/1 twill = lighter, softer, better drape; 3/1 twill = heavier, more durable

Oxford

• Basket weave variation, two yarns in the warp
• Distinctive basket texture, breathable, softens with washing
• The classic button-down shirt fabric (especially oxford cloth)
• 140-200 gsm typical

Poplin

• Fine plain weave with a crisp hand
• Smooth, breathable, wrinkles easily
• Dress shirts, formal wear
• 100-140 gsm typical

Gabardine

• Tight twill weave, steep and durable
• Wool or wool-blend, used for suits and structured garments
• 200-320 gsm

Canvas / duck

• Heavy plain or basket weave
• Very durable, rigid when new, softens with wear
• Workwear, jackets, bags
• 300-600 gsm

Blends: how to read a composition label

Rule of thumb: the higher the poly content, the less the garment shrinks and the more it holds shape. The lower the poly content, the softer and more breathable, but more shrink risk.

The 3 tests to run on every fabric sample

Test 1: Shrinkage test

• Mark a 20 cm x 20 cm square on the fabric before washing
• Wash at 40°C (normal cycle), tumble dry low (or air dry if spec says so)
• Re-measure the marked square
• Acceptable shrinkage: 3-5% for cotton, 1-2% for poly blend, 0-1% for 100% poly
• If shrinkage exceeds 5%, the fabric will not hold size after washing — this becomes a returns problem

Test 2: Opacity / shear test

• Hold the fabric up to a light source
• Light colors under 150 gsm: usually sheer, especially on white fabric
• Dark colors under 200 gsm: often sheer, especially on black fabric
• If opacity matters for your market (premium, European buyers), specify 200+ gsm for light colors

Test 3: Recovery (stretch and bounce) test

• Stretch the fabric 20% and release
• Good recovery: returns to within 5% of original length
• Poor recovery: stays stretched, looks saggy after wear
• Poor recovery usually means low-quality yarn or insufficient elastane

How to specify fabric in your tech pack

A complete fabric spec needs at minimum:

1. Composition: exact percentages (e.g. “100% cotton” or “80% cotton, 20% polyester”)
2. Knit or woven: which construction family
3. Construction type: single jersey, pique, french terry, fleece, 2/1 twill, oxford, etc.
4. GSM: weight per square meter
5. Yarn count: cotton S count (e.g. 32s) or polyester denier (e.g. 150D)
6. Spinning method: carded, combed, or ring-spun (if applicable)
7. Width: fabric width in cm or inches (affects cutting efficiency)
8. Finish: pre-shrunk, enzyme-washed, brushed, mercerized, anti-pill
9. Shrinkage tolerance: usually 3-5% for cotton
10. Mill reference: preferred mill name if you have one

Common fabric mistakes that cost money

1. Specifying only GSM without yarn count: two fabrics at 180 gsm can feel completely different if one is 24s and the other is 40s
2. Not running the shrinkage test: cotton shrinks 3-5%, and the size chart you wrote will be wrong after the first wash
3. Specifying 100% cotton for a garment that will be washed hot: if your buyer washes at 60°C, cotton shrinks more than usual. Consider a blend.
4. Choosing too-light GSM for a dark color: black fabric under 200 gsm is usually sheer on light skin
5. Not specifying fabric width: narrow fabric means more fabric waste per garment, which the factory silently prices in
6. Accepting “same as last time” without re-testing: mills change fabric lots, and the new lot may behave differently
7. Forgetting the finish: pre-shrunk and enzyme-washed add 0.10-0.50 USD/piece but prevent significant returns

FAQ

What is the difference between GSM and fabric weight?

GSM is weight per square meter — a measure of fabric density. Fabric weight per garment is how much fabric one garment uses (typically 150-250 g for a t-shirt, 600-900 g for a hoodie). They are different numbers: GSM describes the fabric, weight per garment describes the garment.

What GSM should I use for a basic t-shirt?

160-200 gsm is the sweet spot for a midweight t-shirt that holds shape and is opaque. Under 150 gsm feels cheap and is see-through on light colors. Over 220 gsm is a heavyweight tee that costs more and feels structured rather than soft.

Why does my fabric feel different from the sample I approved?

Three common reasons: (1) the bulk lot came from a different dye lot with slightly different hand feel, (2) the mill used a different yarn supplier for the bulk lot, (3) you approved a “nice sample” that the factory made with extra-softener finishing not present in bulk. Solution: always run the shrinkage and recovery tests on both the sample and a bulk cut.

Is higher GSM always better?

No. Higher GSM means more fabric per square meter, which usually means more cost and more weight. For performance apparel and summer tees, lower GSM is often correct. Choose GSM based on product intent, not on “higher is better.”

What is the difference between jersey and interlock?

Single jersey is one layer knitted in one piece — it curls at the edges (visible at the hem and cuffs) and can twist after washing. Interlock is two layers knitted together — it does not curl, has a smoother surface, is more opaque, and is better for printing. Interlock costs about 20-30% more than single jersey.

Can I specify a fabric by mill name only?

You can, but mills change lots and blends. Always specify the technical spec (composition, construction, GSM, yarn count) AND the mill name if you have a preference. This way if the mill changes, you have a fallback spec.

How does fabric MOQ work?

Stock fabric: no additional MOQ (the factory already has it). Custom-dyed fabric: mills require 300-500 kg per dye lot. At 180 gsm, 200 g per t-shirt, 300 kg equals roughly 1,500 t-shirts. So custom color usually means a 1,500-piece minimum for one color, unless you pay a small-lot surcharge of 15-30%.

What is “slub” fabric?

Fabric with intentional irregular thickness in the yarn, creating a textured, slightly uneven surface. Common in linen-blend and “vintage” style tees. Costs about 10-20% more than smooth jersey. Popular in the craft brewery and workwear-inspired apparel market.

Does fabric choice affect which decoration methods work?

Significantly: (1) DTG works best on 100% cotton, less vivid on poly blends, (2) sublimation requires 100% polyester, (3) screen print needs a surface that does not stretch too much (fine on woven, can crack on heavy stretch knits), (4) embroidery needs enough body to prevent puckering (very thin fabric needs backing). See our decoration methods comparison for details.

How this fits the buyer journey

Fabric decisions touch nearly every other stage:

• How to Write a Tech Pack — the fabric spec section is where composition, GSM, and yarn count go
• Custom Apparel Pricing — fabric is 50-65% of per-piece cost
• Custom Apparel Sizing — fabric shrinkage affects whether your size chart stays accurate
• Decoration Methods Compared — fabric constrains which decoration methods work
• Sustainable Custom Apparel — organic cotton and recycled poly are fabric choices with trade-offs

How we work at Kemondo

At Kemondo Apparel, every quote includes a full fabric spec (composition, construction, GSM, yarn count, finish) so you know exactly what you are paying for. We maintain stock fabric libraries in 8 common constructions across US, EU, and Asian body sizing, which lets you order 100-500 pieces without custom fabric MOQ. For custom fabric development, we work with 4 mills in Guangdong and Zhejiang and provide lab dips plus shrinkage test reports before bulk. First-time buyers get a free fabric consultation call where we map your product intent to the right GSM, yarn count, and construction — usually saving 15-30% on over-specified fabric costs.

Not sure which fabric to specify? Message us on WhatsApp with your product idea, target market, and price range. We usually reply within 12 hours with 2-3 specific fabric options and a cost comparison.