Fabric and GSM guide for knitwear: jersey, piqué, fleece and what to specify

Fabric is close to half the price of a knitted garment and most of what a customer feels, so the fabric line in your tech pack is the most consequential one you will write. This guide explains the terms a Bangladeshi knit factory will use back to you: GSM, yarn count, single jersey versus interlock, combed versus open-end, the constructions behind t-shirts, polos and fleece, and the tests that tell you whether a fabric will shrink, pill or go see-through before you have bought a thousand pieces of it.

What does GSM mean, and what weight should I choose?

GSM is grams per square metre: the weight of one square metre of the fabric, measured on a conditioned sample under a standard method such as ISO 3801. It is the single most useful number for describing a knit, because it tells you, roughly, how the garment will feel and hang, and it is the number a factory prices from.

Two cautions. GSM is measured on the finished fabric, after dyeing and any brushing, so a “300 GSM fleece” quoted on greige fabric may finish lighter. And the same GSM in different yarns feels different: a 180 GSM combed ring-spun jersey is softer and smoother than 180 GSM open-end. Ask for the weight in the finished state, and ask what yarn it is made from.

Yarn: combed, ring-spun, carded, open-end

Yarn is where the hand-feel of a t-shirt is decided. Ring-spun yarn is twisted from fibres that have been drawn parallel, which makes it smoother and stronger; combed ring-spun goes a step further by removing short fibres before spinning, giving the softest and least pilling-prone surface. Carded yarn skips combing and is slightly rougher. Open-end (rotor-spun) yarn is faster and cheaper to make, and gives a coarser, fuzzier surface that pills sooner; it is common in promotional tees.

Yarn count describes fineness. In Bangladesh you will hear the English cotton count, written like 30s or 40s: the higher the number, the finer the yarn. A 20s or 24s yarn makes a heavier, sturdier jersey; a 30s yarn is the everyday t-shirt standard; 40s and above make lighter, smoother fabrics. Blends are described by percentage, such as 60/40 cotton/polyester, and the elastane in a stretch fabric is usually 5–10%.

Knit constructions, and which garment each one suits

• Single jersey. The basic t-shirt knit: one set of needles, a smooth face and a looped back, lightweight and drapey, with a tendency for the edges to curl. Used for t-shirts, dresses and linings.
• Interlock. Two layers of jersey knitted together so both faces are smooth. Heavier, more stable and more opaque than single jersey at the same yarn, which is why it suits babywear, premium tees and activewear.
• Rib. Alternating raised and sunken columns, with high stretch and recovery across the width. Used for necklines, cuffs and waistbands, and as a garment fabric for fitted tops.
• Piqué. A textured, waffle-like knit that breathes well and holds a collar shape. The polo shirt fabric.
• French terry. A jersey face with loops on the back, absorbent and midweight. Sweatshirts and joggers for warmer climates.
• Fleece. French terry whose back has been brushed to raise the fibres into a soft, insulating nap. Hoodies and heavy sweatshirts.
• Waffle and thermal. A cellular knit that traps air. Base layers and loungewear.

Fibres: cotton, blends and the certified options

Bangladesh’s knit mills run mostly on cotton, and cotton is where the country is cheapest and most consistent. Cotton/polyester blends add durability, reduce shrinkage and cost less; polyester and nylon with elastane are the base of activewear and swimwear, and are more often imported. Organic cotton must be certified to be called organic on a label: under GOTS, the factory’s scope certificate shows it may process certified material, and a Transaction Certificate for your shipment shows your goods were made with it. Recycled polyester and cotton are certified the same way under the Global Recycled Standard. Our sustainable production page explains what each claim needs behind it, and our fabric sourcing page shows which fabrics Bangladesh makes itself and which it imports, which also decides your duty position.

Which fabric tests should I ask for?

Four tests answer the questions that cause most returns, and all four are run on the bulk fabric before cutting on a well-managed order.

Set the acceptable limits in your tech pack rather than leaving them to the factory: a maximum shrinkage per direction, a minimum pilling grade, and the fastness grades your market or retailer requires. Then the test report is a pass or fail against your numbers, not an opinion. Our quality control page explains how fabric is inspected before cutting on the 4-point system and why that inspection is where orders are saved.

How fabric decides your price

A 2023 study of Bangladeshi factory cost sheets put fabric at 42.6% of the FOB price of a basic t-shirt and 52.3% of a polo. Every choice above moves that line: a heavier GSM uses more yarn per piece, combed yarn costs more than open-end, a custom colour needs its own dye lot and its minimum, and certified organic or recycled fibre carries a premium. The cheapest quote for “a 180 GSM cotton tee” is usually a carded or open-end yarn in a stock colour; a good supplier will tell you which. Our cost guide shows the full cost sheet, and the order cost estimator turns a starting price into an order budget.

How to specify fabric in a tech pack

• Fibre composition by percentage, and whether certified (GOTS, OCS, GRS) with a transaction certificate required
• Construction: single jersey, interlock, piqué, French terry, fleece, rib
• Finished weight in GSM, with a tolerance, for example 180 GSM ± 5%
• Yarn: combed ring-spun, carded or open-end, and the count if you know it
• Colour: a Pantone reference or a physical standard, and whether it is a stock shade or a custom dye lot
• Finish: enzyme wash, silicone softener, peached, brushed, bio-polished
• Test requirements and limits: shrinkage, pilling, fastness

Our free tech pack template has a fabric section laid out this way. If you are not sure what to put, send a garment you like and we will describe its fabric back to you in these terms, then send knit-down swatches in the weights you are considering so you can compare hand-feel and opacity before sampling.