Fabric Weight Converter (GSM ↔ oz/yd²)
Convert a fabric's areal weight between the metric GSM and imperial oz/yd² systems, and see which weight band it falls into — the fastest way to compare cloths quoted in different units.
Converted weight
Medium — denim, twill, sateen, jersey
Two units for one property
Fabric weight is an areal density — mass spread over area — and the whole industry measures it, because it predicts how a cloth will drape, insulate, and wear. Mills in metric markets quote GSM; the North American trade and the denim world quote ounces per square yard. They describe exactly the same thing, so a single constant, 33.906, moves cleanly between them.
Knowing both lets you compare a “280 GSM” French terry against an “8 oz” fleece without guessing. The weight class shown alongside the number is a starting point for matching a fabric to a project — always confirm against a physical swatch, since weave, finish, and fibre change how a given weight behaves.
Frequently Asked Questions
What is GSM in fabric?
GSM stands for grams per square metre — the weight of a one-metre-by-one-metre sheet of the fabric. It is the most common way to describe how light or heavy a cloth is, independent of its width, and it is the figure most European and Asian mills print on a spec sheet.
How do you convert oz/yd² to GSM?
Multiply ounces per square yard by 33.906 to get grams per square metre. One ounce is 28.3495 grams and one square yard is 0.83613 square metres, so 1 oz/yd² = 28.3495 ÷ 0.83613 = 33.906 g/m². To go the other way, divide GSM by 33.906.
Is oz/yd² the same as the ounces used for denim?
Yes. When a denim is called '12 oz' or a canvas '10 oz', that is ounces per square yard — the same unit this tool converts. A 12 oz denim is about 407 g/m², firmly in the heavy range.
What GSM counts as lightweight, midweight, or heavyweight?
As a rough guide: under 100 g/m² is very light (chiffon, voile); 100–200 is light (shirting, quilting cotton); 200–340 is medium (denim, twill, jersey); 340–500 is heavy (canvas, upholstery); and above 500 is very heavy. Bands overlap because construction and fibre also matter.
Does a higher GSM always mean better quality?
No. GSM measures weight, not quality. A fine, tightly woven lightweight shirting can be far better made than a heavy but loosely woven cloth. Use weight to match a fabric to a purpose — drape, warmth, durability — rather than as a quality score.
Educational reference only. Weight bands are approximate — the right fabric for a job depends on weave, finish, and fibre as well as GSM. Always check against a physical sample.