GSM (grams per square metre)
A measure of fabric weight expressed as grams per square metre, used to compare how heavy, dense or substantial a textile is.
What it means
GSM tells you the mass of one square metre of the fabric. A higher GSM means a denser, heavier and usually warmer or more durable cloth; a lower GSM means a lighter, more breathable one. It is the standard way towels, sheets and T-shirts are graded.
What to do
Use GSM to set expectations: a 600+ GSM towel is plush but slow to dry, while a 400 GSM towel dries faster. Heavier fabrics generally need a longer drying time and benefit from not being overpacked in the drum.
How to use this term
Use this fabric-care term to understand why the same detergent, heat or stain method can behave differently across fibres.
- Read gsm (grams per square metre) with the other symbols on the same care label; the strictest symbol wins.
- Match the instruction to the garment's most fragile part, including trims, lining, prints and finishes.
- If the label, fabric behaviour and stain method disagree, test a hidden area or choose the lower-risk route.
Common mistake
Do not choose a method only by stain type; fibre, weave, dye and finish can change what is safe.
For the broader method, use the Beginner laundry guide and then return to this term when the label changes the safe option.
Related terms
Sources
- ISO 3801 Textiles — Determination of mass per unit length and mass per unit area — International Organization for Standardization