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Short answer
GSM means grams per square metre, the weight of one square metre of fabric, and it is the quickest guide to how a fabric hangs and how much light it blocks. Sheers are usually under about 120 gsm, everyday dimouts about 150 to 300 gsm, and coated blackouts and velvets over about 300 gsm. GSM does not measure durability; for upholstery, check the Martindale rub count.
What does gsm mean in fabric?
A fabric's weight is given in grams per square metre (gsm, sometimes g/m²). Some suppliers in other markets quote ounces per square yard; 1 oz/yd² is about 34 gsm. A higher number means more yarn, a denser weave, a pile or a coating.
Good to know
GSM is per square metre, not per running metre. A 300 cm wide fabric weighs twice as much per running metre as a 150 cm wide fabric of the same gsm.
What gsm is good for curtains?
| Fabric | Roughly | Example in the JOTEX range |
|---|---|---|
| Sheer and voile | Under about 120 gsm | CALLIE about 89 gsm; VALERY about 106 gsm |
| Blackout lining | About 100 gsm | POSH Creation LINER, 100 gsm |
| Dimout | About 150 to 300 gsm | LAUREN about 225 gsm; COMO about 280 gsm |
| Curtain velvet | About 280 gsm | VELVET and CINEMA |
| Blackout | Over about 300 gsm | TEKUSU ALHAMBRA about 355 gsm; MIDORI about 400 gsm |
| Upholstery velvet | About 450 gsm | YarnGuard PURIFY and REPEL |
| Outdoor acrylic | About 260 to 340 gsm | BREEZE and BRISA about 260 gsm; PATIO about 340 gsm |
Check each collection's page for its listed weight.
What gsm tells you
- Drape: light fabrics float and move; medium fabrics fall in soft, rounded folds; heavy fabrics give full, deep folds.
- Light and heat: heavier, denser fabrics block more of both, though a coating does more than weight alone.
- Track and motor load: the installer needs the gsm, the lining, the fullness and the size to choose a track and motor. See Fabrics for Motorised Curtains.
- Stack-back: heavier curtains stack wider when open.
- Feel and value: at the same weave, more weight usually means more yarn.
What gsm does not tell you
- Durability: for upholstery, the Martindale rub count is the measure. A light, tightly woven fabric can outlast a heavier, loose one. See Martindale Rub Test Explained.
- Opacity on its own: a 100 gsm blackout lining blocks light that a 280 gsm dimout lets through, because of its coating.
- Fade resistance: that is light-fastness. See Light-Fastness Explained.
- Quality: yarn, weave and finish matter as much as weight. See Polyester Curtain Fabric.
Tip
Compare samples of the same type side by side and hold them up to a window. Weight, weave and the light coming through tell you more together than any one number.
Choosing by weight
| Use | Look for |
|---|---|
| Sheer for daytime privacy | Light; check the weave is even |
| Everyday living room curtain | Medium dimout |
| Bedroom that must be dark | Heavy blackout, or any curtain with a blackout lining |
| Tall or motorised curtain | Medium weight; give the installer the gsm |
| Sofa or dining chair | Weight for feel; Martindale for wear |
Frequently asked questions
What does gsm mean in fabric?
Grams per square metre: the weight of one square metre of the fabric.
What gsm is good for curtains?
It depends on the job: under about 120 gsm for sheers, about 150 to 300 gsm for everyday dimouts, and over about 300 gsm for coated blackouts and velvets.
Is a higher gsm fabric better?
Not automatically. It hangs heavier and blocks more light, but weave, yarn and finish matter as much, and durability is measured by rub count, not weight.
What gsm is upholstery fabric?
It varies widely. Performance velvets such as YarnGuard PURIFY and REPEL are about 450 gsm. For wear, check the Martindale rub count.
How do I convert oz to gsm?
Multiply ounces per square yard by about 34. For example, 8 oz/yd² is about 270 gsm.
Curtain maker, upholsterer or designer?
Specifications are public on every collection page. JOTEX dealers can log in for live stock and pricing, and our team can send samples or open a dealer account.