Fabric GSM Calculator

📏 From Swatch to GSM

What is a Fabric GSM Calculator?

GSM — grams per square metre — is the single most useful number for describing a fabric's weight, and it drives everything from how much dye a piece will drink to how it drapes. This calculator takes a measured swatch and turns it into GSM and the imperial oz/yd² figure, so you can compare cloths, confirm a supplier's claim, and plan a dye batch around the real weight of your goods.

Use it to characterise an unlabelled fabric, check a bolt against its spec, or estimate the fibre weight for a depth-of-shade recipe. The results are estimates for planning; test on a sample swatch first, cutting cleanly and weighing on a calibrated scale for the truest reading.

❓ Frequently Asked Questions

How do I calculate fabric GSM from a swatch?

Cut a swatch, measure its length and width in centimetres, and weigh it in grams. The calculator works out the area in square metres — (length ÷ 100) × (width ÷ 100) — then divides the weight by that area to give grams per square metre. A 5 g swatch measuring 20 × 20 cm has an area of 0.04 m² and therefore weighs 125 GSM.

What's the difference between GSM and oz/yd²?

Both describe how heavy a fabric is, just in different units. GSM (grams per square metre) is the metric standard used across most of the textile world; ounces per square yard is the imperial figure still common on US spec sheets. The calculator shows both, multiplying GSM by 0.0294935 to give the oz/yd² value so you can quote whichever your supplier uses.

How accurate is the GSM reading?

These are estimates for planning; test on a sample swatch first. Accuracy depends on a clean, accurately cut swatch and a conditioned weight — moisture, stretched edges, and a wobbly ruler all skew the result, so cut squarely, weigh on a calibrated scale, and average a couple of swatches for a heavier or uneven cloth.