GSM stands for grams per square metre and is the weight of the fabric, measured by cutting a piece of known size and weighing it. For T-shirts, light fabric typically runs about 140 to 160 GSM, standard about 160 to 180 GSM, and heavy about 200 to 240 GSM. Weight is not the same as quality, but it is the first number a factory will quote and the first thing a customer feels, so it belongs in your tech pack alongside yarn count, fabric construction and finish.
What each weight band suits
- Light, about 140 to 160 GSM: promotional and event T-shirts, summer basics, undershirts and layering pieces. The fabric is cheaper and cooler but more transparent, especially in white and pale shades.
- Standard, about 160 to 180 GSM: everyday retail T-shirts and the bulk of what high street brands sell. It drapes well, prints well and has acceptable opacity. Polo pique usually sits a little higher, around 180 to 220 GSM.
- Heavy, about 200 to 240 GSM: boxy streetwear tees, premium basics and workwear. It holds its shape, feels substantial and costs more in yarn and in freight because the garment is heavier.
Weight is only part of the specification
Two fabrics at 180 GSM can feel very different. Yarn count, whether the cotton is combed or carded, ring spun or open end, and the knit structure all change the hand feel, pilling and durability. Finishes such as bio-polishing, enzyme washing or silicone softeners alter the feel without moving the weight much. Specify all of these, not only the GSM.
Set a tolerance as well. Knit fabric varies between rolls and between dye lots, and a tolerance of around plus or minus 5 percent is a common starting point. Ask for GSM to be measured after the fabric has been washed and relaxed, because fabric stretched on the roll reads lighter than it ends up in the finished garment.
How to confirm the factory is delivering it
Ask for a fabric swatch and a test report on the bulk fabric before cutting starts. Have the inspector cut and weigh pieces from several rolls rather than one, and compare the result with the sealed sample. Lowering GSM is one of the easiest ways for a supplier to cut cost without telling anyone, and it shows up later as a thinner garment that shrinks and twists more than the sample did.
Keep the sealed sample and a swatch of the approved fabric with your own team. If a shipment feels wrong, you then have something to measure against rather than an argument about memory.
How we handle it
We write the fabric specification into the order, seal the approved sample, and have GSM checked on bulk fabric before cutting begins. Inline and final inspections include weight and shrinkage checks against that seal, and you get a weekly update while the order runs. If you are unsure which weight your market expects, a free 20-minute sourcing review is a good place to start.