In short
GSM is the weight of a square metre of fabric: about 140–160 for lightweight tees, 180–220 for premium basics, 240–300 for heavyweight, 180–240 piqué for polos and 280–500 brushed fleece for hoodies, measured on finished fabric. Combed ring-spun yarn is softer than open-end, which is more even but weaker. Specify composition, construction, finished GSM with a tolerance, yarn, colour and the shrinkage, pilling and fastness limits to test against.
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GSM is the weight of one square metre of fabric, measured on finished fabric: about 140–160 for lightweight tees, 180–220 for premium basics, 240–300 for heavyweight tees, 180–240 for piqué polos and 280–500 for brushed fleece hoodies. Specify it with a tolerance, together with the composition, construction, yarn and colour, and the shrinkage, pilling and fastness limits to test against. Fabric is close to half the price of a knitted garment and most of what a customer feels, so 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.
| Weight | GSM range | Typical use | What to watch |
|---|---|---|---|
| Lightweight jersey | 140–160 | Promotional tees, warm climates, layering | Can look sheer in pale colours; test opacity |
| Midweight jersey | 180–220 | Premium basics, most brand t-shirts | The usual balance of drape, opacity and cost |
| Heavyweight jersey | 240–300 | Boxy streetwear tees, structured fits | Higher fabric cost per piece; slower to dry |
| Piqué | 180–240 | Polo shirts | Texture size and yarn quality show in the collar |
| French terry | 280–380 | Lighter sweatshirts, joggers | Loop side inside; check loop density |
| Brushed fleece | 280–500 | Hoodies, heavy sweatshirts | Brushing thins the back; confirm GSM after brushing |
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; Cotton Incorporated finds that, spun from the same fibre, it is more even and less hairy than ring-spun yarn, with better abrasion resistance, but 10 to 30% weaker and bulkier. It is common in promotional tees. Our guide to combed, carded and ring-spun cotton explains what each label means and which claims a test report can prove.
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, at 280 to 500 GSM on our bulk hoodie and sweatshirt page.
- Waffle and thermal. A cellular knit that traps air. Base layers and loungewear.
Not sure which fabric to choose?
Send a garment you like or describe the feel you want. We propose fabrics that suit the product, its price and your market.
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.
| What you want to know | Test | Method |
|---|---|---|
| Will it shrink? | Dimensional change after washing and drying | ISO 5077, using the washing procedures of ISO 6330 |
| Will it pill? | Pilling resistance | ISO 12945-2 (Martindale method) |
| Will the colour hold? | Colour fastness to washing, rubbing, perspiration and light | The ISO 105 series |
| Is it the weight I ordered? | Mass per unit area | ISO 3801 or an equivalent method, on finished fabric |
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 quoted 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 as a reference, and ask for knit-down swatches in the weights you are considering so you can compare hand-feel and opacity before sampling.
Questions buyers ask.
Is 180 GSM good for a t-shirt?
For most brand t-shirts, yes. 180 GSM sits at the bottom of the midweight band of roughly 180 to 220 GSM, which is the usual balance of drape, opacity and cost for premium basics. Below it, 140 to 160 GSM jersey suits promotional tees, layering and warm climates, but can look sheer in pale colours. Above it, 240 to 300 GSM gives the boxy, structured feel of streetwear tees at a higher fabric cost per piece. Two things matter as much as the number. First, weight should be measured on the finished fabric, after dyeing, so ask for finished GSM with a tolerance such as plus or minus 5%. Second, the yarn changes the feel: 180 GSM combed ring-spun jersey is softer and smoother than 180 GSM open-end. The cheapest quote for a 180 GSM cotton tee usually uses carded or open-end yarn in a stock colour.
What is the difference between GSM and yarn count?
They describe different things, and a good fabric specification gives both. GSM is the weight of one square metre of finished fabric, measured under a standard method such as ISO 3801. It tells you roughly how the garment will feel and hang, and it is the number a factory prices from. Yarn count describes how fine each thread is. In Bangladesh you will usually hear the English cotton count, written as 30s or 40s, and the higher the number, the finer the yarn. A 20s or 24s yarn makes a heavier, sturdier jersey, 30s is the everyday t-shirt standard, and 40s and above make lighter, smoother fabrics. Because the two are separate, two fabrics of the same weight can still feel different. Put the finished GSM with a tolerance in your tech pack, add the yarn type and count if you know them, and if you do not, ask the factory to state them in its quote.
Why do some t-shirts pill, and how can I avoid it?
Pilling is the small balls of fibre that form on a surface that rubs, and the yarn decides most of it. Open-end, or rotor-spun, yarn is fast and cheap to make, which is why it is common in promotional tees; it is less hairy than ring-spun yarn but 10 to 30% weaker, so fibre quality and finishing matter too. Ring-spun yarn is smoother and stronger, and combed ring-spun, which has the short fibres removed before spinning, gives the surface least prone to pilling. To avoid surprises, write the yarn type into your tech pack instead of leaving it to the factory, and set a minimum pilling grade. The recognised test is ISO 12945-2, the modified Martindale method, and on a well-managed order it is run on the bulk fabric before cutting. The report then becomes a pass or fail against your number rather than an opinion. Ask for knit-down swatches in different yarns so you can compare surfaces before sampling.
Sources
Checked . Rules and figures change, so confirm anything that affects your pricing.
- ISO 3801:1977 — Textiles: determination of mass per unit length and mass per unit area (opens in a new tab)
- ISO 6330:2021 — Textiles: domestic washing and drying procedures for textile testing (opens in a new tab)
- ISO 5077:2007 — Textiles: determination of dimensional change in washing and drying (opens in a new tab)
- BSI — BS EN ISO 12945-2:2020, determination of fabric propensity to surface pilling (modified Martindale method) (opens in a new tab)
- Rajib et al. (2023) — Complete Garment Costing with Major Cost Breakdown, Journal of Textile Science and Technology, 9, 115–126 (opens in a new tab)
- Global Organic Textile Standard — public database and transaction certificates (opens in a new tab)
- Cotton Incorporated: TRI 1004, introduction to open-end spinning (open-end vs ring yarn: more even, less hairy, better abrasion resistance, 10% to 30% weaker) (opens in a new tab)