Fabric GSM Calculator (from Sample Weight)

How it works

GSM = swatch grams ÷ swatch area (cm²) × 10,000 (round 100 cm² cutter: grams × 100); oz/yd² = GSM ÷ 33.906; g per linear metre = GSM × width (m); roll GSM = net kg × 1,000 ÷ (length × width)

Grams per square metre is the universal measure of fabric weight and the quickest proxy for its hand, opacity and use: 120–150 for shirting, 160–180 for a T-shirt, 300+ for denim and fleece. The standard test cuts a 100 cm² disc with a circular GSM cutter and weighs it — the grams times 100 are the GSM — but any accurately measured rectangle works, and a whole roll’s net weight divided by its area gives the same answer for goods already in stock. The American ounces per square yard is 33.9 g/m², not to be confused with ounces per linear yard, which depends on width. Weight per linear metre matters for costing, shipping and for converting between roll weight and roll length; humidity changes fabric weight by a few percent, so samples are conditioned before weighing.

Worked example

A 100 cm² round swatch weighing 1.85 g is 185 GSM — 5.5 oz/yd², a heavier T-shirt or light sweatshirt weight. At 150 cm width that is 278 g per linear metre, so a 50 m roll weighs about 13.9 kg plus the tube.

Frequently asked questions