The number on a fabric specification sheet that most people ignore turns out to be one of the most useful pieces of information about any garment. GSM, grams per square metre, is simply how much a square metre of fabric weighs. Higher means heavier and denser. Lower means lighter and thinner.
For joggers and sweatpants specifically, this number matters more than almost any other specification.
Why Weight Is Not the Same as Warmth
A common misunderstanding is that heavier fabric is simply warmer fabric. This is partially true but not the whole picture.
Fabric weight affects warmth, yes. But it also determines durability, structure, how a garment moves, and how it survives repeated washing. A 150gsm cotton jersey feels acceptable on the hanger and starts betraying itself within weeks of regular wear. The fabric thins. The structure collapses. The knees go baggy, the seat sags, and what looked like a reasonable purchase starts looking like something that should have been thrown out last season.
A 330gsm fabric has enough density to hold its structure through hundreds of wash cycles. The fibres are packed more tightly. There is less space for the fabric to thin or distort. The result is a garment that looks and feels substantially the same in year two as it did in year one.
The Practical Breakdown
Under 200gsm: Budget and fast fashion joggers. Fine for summer, inadequate for autumn and winter. Thin out quickly. Lose shape quickly. Often feel overstretched at the knee after heavy use.
200 to 280gsm: Mid weight. Decent quality. Works across more of the year but still shows its limits in cold weather or with heavy use. The majority of mid-priced high street joggers fall here.
300gsm and above: This is where joggers start to feel like a considered purchase. The fabric has body. It drapes properly rather than clinging. It insulates without feeling heavy. It holds its shape through washing in a way that lighter fabrics cannot.
330 to 350gsm: The upper end of practical jogger weight. Heavy enough to feel substantial, still light enough to wear comfortably for extended periods. This is where most premium loungewear and quality casualwear sits.
What GOTS Certified Means for Fabric Weight
A 330gsm conventional cotton jogger and a 330gsm GOTS certified organic cotton jogger weigh the same. The certification is not about weight, it is about how the cotton was grown and processed.
GOTS, the Global Organic Textile Standard, covers the entire supply chain from organic farming without synthetic pesticides or fertilisers through to the processing, dyeing, and manufacturing stages. It is independently audited at each stage rather than self certified by the brand.
For the person wearing the garment, organic certification means no residual synthetic chemicals in the fabric against your skin. For the environment, it means significantly lower pesticide load in the farming stage and tighter controls on chemical inputs throughout processing.
The weight tells you how the garment will feel and last. The certification tells you what went into making it.
Our Numbers
Our slim fit joggers are 330gsm GOTS certified organic cotton, made in London. Our deadstock sweatpants are 340gsm GOTS certified organic cotton, also made in London, loose fit, grey marl only.
Both are single fibre construction throughout. The sewing threads are cotton. The elastic is natural rubber. Nothing synthetic anywhere in the construction, which matters when the garment eventually reaches the end of its life and needs to be recycled.
The number is 330. Now you know what it means.
Leave a Reply