GSM: The Only Fabric Number That Matters
One number tells you if a shirt is trash or a keeper — here's how to read it.
Grounded in the research on grammage
Pre-Industrial Roots
Weavers and merchants have measured cloth weight since the medieval wool trade. The English assessed fabric by the ounce per yard; the French by grams per square meter. When metric industrialization swept Europe in the 1800s, g/m² — grams per square meter, or GSM — became the standard because it's area-normalized. A yard of fabric and a meter of fabric aren't the same size. A square meter always is. That consistency made GSM the global baseline.
20th-Century Standardization
ISO 536, first published in 1976, formally codified GSM as the international standard for measuring the mass of sheet materials including textiles and paper. The test is dead simple: cut a 100cm² swatch, weigh it on a precision scale, multiply by 100. That's your GSM. The same method applies to a cashmere hoodie and a shipping envelope. No proprietary equipment, no black box — just mass and area.