Specification · 4 min · Updated September 2026

GSM or Weight per Metre: How to Specify Fabric Weight Without Confusion

The short answer

GSM is the weight of one square metre of fabric. Weight per metre (sometimes GLM) is the weight of one running metre at the fabric's full width. To convert, multiply GSM by the width in metres: a 150 GSM fabric at 58 inches (1.47 m) weighs about 221 grams per running metre. Always state the width alongside a per-metre weight, because without it the figure means nothing.

Two ways of saying the same thing

GSM (grams per square metre) describes the cloth independent of its width, which makes it the fairest way to compare two fabrics. Weight per running metre describes what a metre off the roll actually weighs, which is how many mills and traders count and invoice. Neither is wrong. Problems start when one party quotes one and the other assumes the other.

The conversion

Weight per metre (g/m) = GSM x width in metres
GSM = weight per metre / width in metres
1 inch = 0.0254 metres, so 58 inches = 1.47 m and 60 inches = 1.52 m
Ounces per square yard (used in canvas and denim) = GSM / 33.9

Quick reference

GSM	At 44 in (1.12 m)	At 58 in (1.47 m)	At 63 in (1.60 m)
100	112 g/m	147 g/m	160 g/m
150	168 g/m	221 g/m	240 g/m
200	224 g/m	295 g/m	320 g/m
300	336 g/m	442 g/m	480 g/m
400	448 g/m	589 g/m	640 g/m

How to check what you received

Cut an exact 10 cm x 10 cm square from the body of the fabric, away from the selvedge, and weigh it on a scale that reads to 0.01 g. Multiply the reading by 100 to get GSM. Repeat on three pieces from across the width and average them. For weight per metre, weigh a measured length at full width and divide by the length.