Added 2026-10-10 from trending overseas buyer search questions. We update this centre daily.
Buyers often specify a fabric by weight alone: "120 GSM poplin, please." But GSM is a mass measurement — grams per square metre — and it says nothing about how that mass is arranged. Two cloths can share one GSM and still be different products in opacity, tightness and hand. One may be built from many fine, high-count yarns packed close together; the other from fewer, coarser yarns set openly apart. The first blocks light and feels smooth; the second lets light through and feels loose. The property that decides this is cover factor.
Cover factor is the trade's way of describing how much of the fabric's surface area is actually occupied by yarn rather than air. It combines two things into one figure: how thick each yarn is (the yarn count) and how many yarns are packed in per inch in each direction (ends per inch in the warp, picks per inch in the weft). A high cover factor means the surface is nearly full and very little of it is air; a low one means an open, breathable cloth with visible gaps.
For a woven cloth there are two cover factors — warp and weft:
| Direction | Formula (cotton system) |
|---|---|
| Warp cover factor | EPI ÷ √(warp Ne) |
| Weft cover factor | PPI ÷ √(weft Ne) |
where EPI/PPI are threads per inch and Ne is the cotton yarn count. The combined cloth cover factor (Peirce, cotton system) is:
Cloth CF = Warp CF + Weft CF − (Warp CF × Weft CF) ÷ 28
In this convention 28 is treated as "full cover". Other yarn-counting systems use different constants, so the absolute number only means something once you know which formula a supplier is quoting.
Using the common cotton-system Peirce bands as a reference, cover factor maps roughly to cloth type:
| Cloth cover factor | Character | Typical fabric |
|---|---|---|
| Below 12 | Very open | Voile, scrim, mulmul |
| 12 – 16 | Open | Light shirting, summer wovens |
| 16 – 22 | Medium | Poplin, cambric, sheeting |
| 22 – 28 | Tight | Denim, twill, workwear |
| Above 28 | Very tight | Canvas, duck, technical cloth |
These are illustrative reference bands, not a pass/fail line. For plain-weave cotton shirting, pushing the combined cover factor much above roughly 24–26 is where many mills start seeing reed marks, end breakage and pick bunching; twill and satin weaves sustain a somewhat higher cover before faults appear because their longer floats mean fewer interlacement points per area.
Do not rely on GSM alone for an opacity- or tightness-critical garment. Ask for the full construction — yarn count plus EPI and PPI — so the mill cannot meet your weight with an open construction that looks or behaves differently. Judge a pale shade on a physical swatch held over skin, not over paper. If you need a target cover factor, tell the supplier the end use and let them recommend a workable count-and-density combination.
We weave to construction in-house, so yarn dyeing, weaving, piece dyeing and finishing sit on one site and a development can be tuned by density as well as weight. Our standard woven range (poplin, twill, canvas, oxford, chambray, yarn-dyed shirting and more) is built to customer construction. For a given order we confirm the achievable construction and cover factor in writing — specific targets are available on request at enquiry. Minimum order is 2,000 metres per colour; sampling is charged and credited against the bulk order; lead time is confirmed in writing at enquiry. Certifications held include OEKO-TEX, GRS, GOTS, OCS and BCI (certificate numbers available on request). Send your construction and end use to gxy@ntboerli.com or open the quote request.
No. It means a tighter, more closed cloth. A high cover can restrict dye penetration and leave a harsher hand; an open, low-cover cloth is chosen deliberately for breathability. The right cover follows the end use, not a score.
Yes, easily. GSM is total mass per square metre and says nothing about how that mass is distributed. A fine, high-count cloth set densely and a coarse, openly-set cloth can weigh the same yet one blocks light and the other shows through. Always ask for yarn count and EPI/PPI alongside GSM.
For a white or pale shirting you generally want enough cover to avoid show-through — typically the medium-to-tight cotton-system band rather than the open one. The exact construction is set by yarn count and density, so we confirm a workable construction against your target at enquiry (available on request).
No. The figure depends on the yarn-counting system and the convention used (the cotton/Peirce system treats 28 as 'full cover'). Always confirm which formula a supplier quotes before comparing numbers across mills.