AA Enterprises · Buyer Tools
Woven Cover Factor Calculator
Estimate warp, weft and cloth cover factor for a woven construction (English/cotton system).
Warp CF = EPI ÷ √(warp Ne); Weft CF = PPI ÷ √(weft Ne). Cloth CF = warp + weft − (warp × weft) ÷ 28 (Peirce, cotton system). Max practical cloth CF is around 28.
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Cover factor measures how much of the fabric area is actually occupied by yarn rather than air. It combines thread density and yarn thickness into one number, which is why two fabrics with the same EPI can feel completely different.
Higher cover means a tighter, more opaque, more wind-resistant fabric. Lower cover means an open, breathable, lighter cloth.
Reading the number
These bands use the Peirce cotton cover factor convention. Other conventions produce different absolute numbers, so always confirm which formula a supplier is quoting.
| Cover factor | Character | Typical fabric |
|---|---|---|
| Below 12 | Very open | Voile, mulmul, scrim |
| 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 fabric |
Practical consequences
Cover factor drives more than handle. Very high cover restricts dye penetration and can leave a fabric harsh and slow to finish. Very low cover shows seam slippage and poor abrasion resistance.
On weaving, cover factor also sets a practical ceiling. Push it too high for the yarn count and the loom cannot beat the weft in cleanly, which shows up as bar marks and weaver complaints.
Frequently asked questions
What is cover factor in fabric?
A measure of how much of the fabric area is occupied by yarn rather than air, combining thread density and yarn thickness into one figure.
What is a good cover factor?
It depends on end use. Poplin and sheeting sit around 16 to 22, denim and twill 22 to 28, and voile below 12.
Does higher cover factor mean better fabric?
No, just tighter. High cover can restrict dye penetration and give a harsh hand; open fabrics are chosen deliberately for breathability.
How does cover factor affect weaving?
Beyond a certain cover the loom cannot beat the weft in cleanly, causing bar marks. There is a practical ceiling for every yarn count.
Can you advise on yarn for a target cover factor?
Yes. Tell us the construction and target cover and we will recommend counts that weave cleanly and quote them.