Fabric weight (GSM) explained

Fabric weight tells you how many grams one square metre of fabric weighs. It is written as g/m² or GSM. For woven fabrics it is measured according to ISO 3801: a sample of precisely known area is conditioned, weighed and the result converted to a square metre.

What fabric weight changes

Fabric weight is the result of several decisions at once: how thick the yarn is, how densely the fabric is woven and in which weave. So two fabrics of the same weight can feel different – and two fabrics of the same fibre at different weights are, in reality, different products.

In practice, fabric weight mainly affects:

• Drape and heft. A heavier fabric "falls" better – a tablecloth, a curtain, a heavy linen throw.
• Warmth. More material means more air trapped in the fabric; heavier fabrics are generally warmer.
• Translucency. Lightweight linens and muslins let light through.
• Drying time. More material holds more water.

Typical ranges

Specific values vary between manufacturers and are not set by any standard. Rather than figures that would invite false precision, we give a relative order: muslin and batiste are among the lightest, percale and sateen for bed linen sit in the middle, linen bed linen tends to be a little heavier than cotton, kitchen linen, twill and denim heavier still, and terry towels are among the heaviest everyday household textiles.

If a specific figure matters to you, compare weights within one type of product, not across categories.

How to check it

Cut (or ask the retailer for) a sample of precisely measured area, for example 10 × 10 cm, which is 0.01 m². Weigh it on accurate scales and multiply the result by a hundred. A sample weighing 1.5 g corresponds to a fabric weight of 150 g/m². The result will only be approximate – laboratory measurement accounts for humidity, which noticeably changes the weight of natural fibres.

Fabric weight and quality

A higher weight does not mean a better fabric. A heavy sheet made from short fibre can be rougher and breathe less well than a lighter percale made from long-staple cotton. Fabric weight helps answer the question "will it be light or heavy?" – the question "will it last?" is answered rather by staple length, the yarn and the weave.