Fabric Weight Explained: GSM, oz/yd² and Grams per Running Metre

What is GSM?

GSM stands for grams per square metre. Cut a piece of cloth exactly one metre by one metre, put it on a scale, and the reading in grams is the GSM. It is the one number on a specification that tells you how heavy a fabric will feel and how much of it you get for a kilogram of yarn. A shirting cloth and a trouser cloth can share a fibre and a weave and still be told apart by GSM alone.

GSM and ounces per square yard

Buyers in the United States quote fabric weight in ounces per square yard, written oz/yd². The two units measure the same thing on different squares, so the conversion is a single division. One ounce per square yard is 33.906 grams per square metre.

The shirting and canvas rows are round figures to show the scale. The BTC-9112 row is from the tag on one of our sample garments.

From GSM to the weight of a running metre

A roll is sold by the metre but woven and often priced by the kilo, so you need the weight of one metre of roll, which depends on the width. Multiply the GSM by the width in metres. BTC-9112 is 214 GSM and 55 to 56 inches wide, which is 1.40 to 1.42 metres, so a running metre weighs 299 to 304 grams. Divide 1000 by that and a kilogram of the cloth is about 3.3 metres. The same arithmetic on a 44-inch cloth at the same GSM gives 239 grams a metre and 4.2 metres a kilo. Our GSM converter does this for any width.

Reading weight on a specification

The specification lines on our product pages give count, construction and width, which is how a weaver describes the cloth. Count and construction together set the GSM, because a finer yarn woven at the same density weighs less, and the same yarn packed more densely weighs more. That link is explained in how to read a woven fabric specification. When a page does not show a GSM, ask for it in the enquiry and quote the garment you have in mind, because the useful question is whether the weight suits the garment.