Specification guide · 7 min read
What GSM means when you order in bulk
By Dinesh Chhabra, CEO, Vidhi Fabrics · Published · Updated
GSM (grams per square metre) is a fabric’s weight, not its quality. The figure a mill quotes and the figure you receive can legitimately differ — greige versus finished cloth, humidity and lot variance all move it — so agree a tolerance and a direction in writing, and check it with a cutter or a weighed 10x10cm square.
GSM is the number buyers quote most often and argue about most easily. It is a useful figure and a narrow one: it tells you what a cloth weighs over a fixed area and nothing else. Most weight disputes are not really about weight — they are about a figure that was never defined, never toleranced, and never checked the same way by both sides. This guide covers what the number does and does not carry, why the mill’s figure and yours can legitimately differ, and how to write it on an order so it means the same thing to everybody.
GSM is a weight, not a grade
GSM is grams per square metre. It describes how much a cloth weighs over a fixed area, and that is the whole of it. It is not a quality score, and a higher number is not a better fabric.
The right number is the one the end use needs. A shirting at 120 GSM and an upholstery cloth at 400 GSM are each correct for their purpose and each useless for the other. Most arguments about weight are really arguments about fitness for use that nobody wrote down.
So ask what the cloth has to do before asking what it should weigh. The answer to the first question narrows the second to a range, and a range is what you should be specifying anyway.
Why the weight you specify and the weight you receive differ
Greige cloth and finished cloth do not weigh the same. Washing, singeing, mercerising, calendering, dyeing and coating each move the figure, some up and some down. A mill quoting greige weight and a mill quoting finished weight are not quoting the same thing, and two quotations are not comparable until you know which is which.
Moisture accounts for more than most buyers expect. Cotton and viscose hold atmospheric moisture, so the same roll weighs differently in a humid Surat monsoon and a dry north Indian winter. Laboratory figures are taken at conditioned humidity; a weighing on a warehouse floor is not, and the gap between them is real rather than anybody’s error.
Loom and lot variance covers the rest. Tension, pick density and yarn batch all shift a little across a production run and more between runs. This is ordinary, it is why a single figure is a target rather than a promise, and it is the reason the next section matters more than this one.
Agree a tolerance, not just a number
Write the weight as a figure with a stated tolerance, or as a range. In the trade it is usually expressed as a percentage either side, and around five per cent is a figure often used — but the number matters far less than the fact that it was agreed rather than assumed. A tolerance nobody recorded becomes an argument the first time a lot lands light.
Say which direction matters to you, because they are different instructions. A garment maker costing yardage per piece usually cares that the cloth is not heavier than specified. A buyer worried about handle and opacity cares that it is not lighter. A supplier cannot infer which one you meant, and will not guess the same way you would.
Keep it with the rest of the specification, against the product code both sides use, so the weight cannot drift away from the sample it was agreed alongside.
How to check the weight when the lot arrives
A GSM cutter takes a disc of 100 square centimetres. Weigh the disc in grams and multiply by 100 to get grams per square metre. Without a cutter, cut a square of 10 by 10 centimetres as accurately as you can, weigh it on a scale that reads to a hundredth of a gram, and multiply by 100. The arithmetic is identical; the error moves into the cutting.
Take several samples rather than one. Weight varies across the width and along the length, so sample near both selvedges and near the middle, and from more than one roll. One disc from the end of one roll tells you about that disc.
Record the average and the spread, not just the average. A lot that averages the specified weight with a wide spread is a different problem from a lot sitting consistently under it, and the two lead to different conversations with the supplier.
Written on the order, that can be one line: “±5% tolerance on weight, tested to ISO 3801, disputes settled against the approved sample.” The number, the standard and the reference for a dispute all sit in the same sentence.
Where GSM stops telling you anything
Two fabrics at the same weight can behave nothing alike. Yarn count, weave, twist and finish decide drape, opacity, handle and how the cloth takes a dye, and none of them appear in the weight. A loosely woven 140 GSM cloth in a coarse yarn and a tightly woven 140 GSM cloth in a fine one are not substitutes, whatever their specification sheets have in common.
This is why an approved sample outranks a number. The specification lets you shortlist candidates and hold a supply to account afterwards; the physical cloth is what tells you whether it is right in the first place. Use the figure to narrow the field and the sample to decide.
With polyester sarees, weight is never the only question: drape and finish matter as much. To see current designs before you decide, start from our polyester sarees wholesale page.
What to put on the order
Five lines, and the weight stops being a source of argument.
- The weight, and whether the figure is greige or finished
- The tolerance, as a percentage either side
- Which direction of variance matters to you, and why
- The product code the approved sample sits against
- How the weight will be checked on arrival — against ISO 3801 — and by whom
Frequently asked questions
- Is a higher GSM better quality?
- No. GSM is a weight and quality is a judgement about construction, yarn and finish. A heavy cloth woven from poor yarn is a heavy poor cloth. Weight only tells you whether a fabric is suited to the use you have in mind.
- Why do two suppliers quote different GSM for what looks like the same fabric?
- Usually because one figure is greige and the other finished, or because they were measured under different humidity, or because one is a nominal specification and the other an actual weighing. Ask which of those a number is before treating two quotations as comparable.
- Can I check GSM without a GSM cutter?
- Yes. Cut a 10 by 10 centimetre square, weigh it on a scale reading to a hundredth of a gram, and multiply by 100. The method is sound; the accuracy depends entirely on how squarely you cut, so take several samples and average them.
- The lot is within tolerance but feels wrong. What now?
- Then weight was the wrong thing to have specified on its own. Handle comes from yarn and construction, so the conversation has to move to those and to the approved sample rather than to the number. It is also the argument for approving a physical sample instead of a specification sheet.
