GSM decides drape, cost and end-use before a single loom starts.
GSM — grams per square metre — is the single most quoted number in a woven fabric spec. Yet it is also the most misunderstood. Here is how we think about it at the mill.
GSM stands for grams per square metre. It is the weight of one square metre of fabric, measured in grams. A light shirting poplin might sit around 90–110 GSM; a heavyweight canvas for workwear can reach 400 GSM and beyond. Everything you feel when you pick up a fabric — its body, its drape, its structure — is mostly GSM speaking to you before you even look at the construction.
For a buyer, GSM matters three times over: it determines end-use (will this hold a tailored shape or fall like a blouse?), it drives cost (heavier means more fibre, more yarn, more loom time), and it is the first thing an inspector checks against your spec sheet.
How GSM is actually measured
In our in-house lab, the test is simple and repeatable:
- A circular cutter stamps out a sample of exactly 100 cm² of fabric.
- The sample is weighed on a calibrated scale.
- The reading is multiplied by 100 to give grams per square metre.
Because a single sample can be skewed by a thick yarn or a local weave variation, we test multiple samples across the fabric width and average them. That is the difference between a number on a datasheet and a number you can build a costing on.
GSM vs weight per metre — do not mix them up
A common error in sourcing conversations is quoting weight per running metre instead of GSM. Weight per metre depends on fabric width: 200 GSM in 150 cm width weighs 300 g per running metre, while the same 200 GSM at 120 cm weighs only 240 g. At Yoga Fabrics we weave up to a maximum width of 59 inches (150 cm), so when we quote, we always quote GSM — width-independent, and comparable across mills.
What each GSM range feels like
These are working ranges, not gospel — construction and finish shift the feel within each band:
| GSM range | What it feels like | Typical end-uses |
|---|---|---|
| 40–70 | Sheer, translucent, airy | Voiles, fine blouse weights, linings |
| 70–110 | Light, crisp, structured | Poplin, fine shirting, summer tops |
| 110–160 | Mid-weight, versatile | Classic shirting, light bottoms, dresses |
| 160–230 | Substantial, holds a line | Twill, chino, soft canvas, skirts and trousers |
| 230–350 | Heavy, rugged | Canvas, denim weights, jackets, workwear |
| 350–600 | Very heavy, technical | Heavy canvas, bags, upholstery-weight, industrial |
At the mill we weave the full span — from 40 GSM up to 600 GSM, with yarn counts from 6s to 100s Ne. The same factory that runs a gossamer voile can run a 500 GSM technical canvas; that breadth is unusual, and it is why GSM conversations at our desk always start with end-use, not with a number.
The GSM question to ask your mill
When a supplier quotes you a fabric, ask two things:
- What tolerance do you weave and test to? A responsible mill tests every lot and keeps GSM within a narrow band, typically ±3–5%.
- How many samples went into that average? One cutter stamp is a guess; multiple samples across the width are a measurement.
Our QC lab tests count, GSM, colour fastness and shrinkage on every production lot — the numbers in our spec sheets are measured, not estimated. The same discipline applies to sustainability claims: if the programme is organic or recycled, ask which scheme covers it, and our guide to GOTS, OCS, GRS and OEKO-TEX sets out what each one actually certifies.