How to Spec Fabric Weight for a Wholesale Order Without Guessing
Fifteen grams per square metre sounds like a rounding error until you multiply it out. On a 12,000-metre order at 150 cm width, that gap is 270 kilograms of cotton that was paid for and never arrived.
The gap opens because most weight lines on a spec sheet carry one number and nothing to check it against: no tolerance, no test method, no stage in the process where the fabric is actually weighed. Orders ship, two scales disagree, and neither side holds a document that ends the conversation. Here is how we write the weight line at BenClothing, and what to add when the cloth comes from a mill we do not control.
Most weight lines carry one number and nothing to check it against.
Take a line that looks perfectly normal on paper: heavy washed cotton twill, 300 gsm. Six words, and four things missing from them.
- No tolerance. A mill landing at 285 g/m² is inside that spec, and so is the buyer who expected 300.
- No test method. A 100 cm² swatch cut near the selvedge and a full-width sample can disagree by 10 grams without anyone behaving badly.
- No stage. Greige, finished and washed cloth are three different numbers for the same roll of fabric.
- No sampling plan. One swatch off one roll tells you nothing about the other 39 in the bale.
None of that makes the line useless. It makes it a starting point instead of a contract. The difference only shows up months later, in a warehouse, when someone has to decide who pays.
Three ways to write it: trade word, single number, full spec
Every weight line you will ever receive sits in one of three buckets. What changes is how much of the argument each one closes before shipment.
| How the line reads | What it protects | What stays open | Reasonable when |
|---|---|---|---|
| Heavy washed twill | Nothing a scale can settle | Weight, tolerance, method and stage, all four | Repeat of a proven style, same mill, counter sample signed by both sides |
| 300 gsm cotton twill | The rough category | A mill sitting 15 grams light inside the grey zone, plus method and stage | Lab dips and counter samples both sealed, order running on the same looms |
| 280 g/m², give or take 5 percent, tested to ASTM D3776 on finished washed cloth, one test per dye lot | The argument itself | Very little, provided the sampling plan is written too | First order, a second source for a running style, or a repeat that crosses seasons |
The trade word is not a mistake. Between a buyer and a mill that have run the same cloth for years, “heavy washed twill” points at a counter sample both sides already signed, and everyone saves the cost of testing something nobody is disputing. Precision should scale with exposure: a repeat of a proven style risks little, while a first order from a new mill risks the entire purchase order.
This is landing harder on desks right now. Enquiries have drifted away from new prints and toward finer yarn counts and tighter weave specs, and buyers increasingly ask for colour fastness, pilling and shrinkage reports before they ask about design at all. A weight line with no method and no stage cannot answer that request, because there is nothing to send back.
Tolerance: where five percent comes from
Yarn count moves between bales, take-up in weaving pulls the cloth in, and finishing pressure pushes it back out. A plain weave can be held tight because the structure is simple. A heavy brushed twill cannot, because brushing removes fibre from the surface after the cloth is already formed. A five percent band is roughly what a mill will put its name to on workwear twill and canvas.
Demand tighter and you are no longer buying fabric, you are buying yarn at a price that has to absorb the rejects. Ask for a two percent band and a mill will either decline or quietly add the cost of the rolls it expects to lose.
One trap catches more buyers than any other: grams per square metre is width-independent, weight per linear metre is not. Cloth at 300 g/m on a 150 cm roll is 200 g/m². The same 300 g/m on a 160 cm roll is 187 g/m². Written the second way, a spec quietly accepts a lighter cloth and calls it compliant. Denim runs into the same wall from the other direction: one ounce per square yard is about 34 grams per square metre, so 12 oz lands near 407 g/m², but an ounce quoted per linear yard changes with the width it is cut from. Any time a supplier gives you ounces without saying which yard, ask before the PO, not after the container.
Weigh the fabric after wash, not before it.
Washing rearranges the same yarns into a smaller area, and weight per square metre reads that as a gain. Cloth that shrinks 3 percent in both directions sits in roughly 6 percent less area, so its grams per square metre climb by about the same 6 percent. A pre-wash 300 becomes 318 after the wash. A post-wash 300 left the mill at something near 283 in greige.
Both numbers are honest. The missing word is the stage, and without it two labs can test the same dye lot and report figures 35 grams apart with clean consciences. Write the stage once and make the counter sample follow it. When we put a garment wash on a style in our Shishi workshop, the stage goes on the same line as the number, so nobody has to guess what “300” was measured on.
What the missing fifteen grams costs
Run the arithmetic on the opening example. A 12,000-metre order at 150 cm width is 18,000 square metres of cloth. Fifteen grams light on every square metre of it is 270 kilograms of fibre you paid for and did not get. Re-weaving a heavy twill takes weeks rather than days, so the realistic choice on arrival is a rebate or an acceptance, and both of them move the delivery date on the styles downstream.
Spread the same 15 grams across four styles in a season and the line item stops looking like rounding. The fix is one rewritten sentence on a spec sheet, and the reason to rewrite it now is that the person who tests your goods next year will be reading that sentence, not the emails around it. If you want a reference for how much detail belongs on a pack, our piece on the lines a tech pack should never leave blank covers the same ground from the workshop side.
FAQ
Can we check fabric weight in-house without sending it to a lab?
A 10 cm square template and a scale that reads to 0.1 g are enough for screening. Cut three swatches from three places across the roll, weigh each, and multiply the average weight in grams by 100 to get grams per square metre, so a 3.1 g swatch reads 310 g/m². Treat it as a filter, not as evidence: for a commercial claim, the method written on the spec is the one a buyer will accept.
Which stage goes on the spec when the cloth is washed?
One stage, stated explicitly, and the counter sample has to follow it. If a wash shrinks cloth by 3 percent each way, testing greige against a sample measured after wash moves the same fabric by about 6 percent per square metre, which is enough to fail a spec the mill actually met.
Read your own spec sheet the way a mill would read it. If the weight line says 300 gsm and stops there, ask who pays when the scale reads 265. We would rather settle that on paper in October than at the warehouse door in January, which is why spec reviews happen before the PO at our workshop and not after the inspection. Send us a spec and our team will answer within 24 hours.