Cover factor is one of the most useful numbers in weaving — it tells you how tightly a fabric is packed, independent of count. Here is how it works.
What cover factor measures
Cover factor combines thread density (EPI/PPI) with yarn coarseness (count) into a single figure for how much of the fabric area the yarn covers:
- Warp cover factor = EPI ÷ √(warp Ne)
- Weft cover factor = PPI ÷ √(weft Ne)
- Cloth cover factor = warp CF + weft CF − (warp CF × weft CF) ÷ 28
Do it instantly with our Cover Factor Calculator.
Why it matters
Cover factor predicts how a fabric will behave: a low value gives an open, light, airy cloth; a high value (approaching the practical maximum of ~28) gives a dense, firm, sometimes stiff fabric that can be hard to weave. It helps you compare constructions and hit a target hand and weight — alongside GSM.
Cover factor and construction
Because cover factor ties together EPI, PPI and count, changing any one shifts it. Planning a reed for your EPI? Use the Reed Count Calculator. For the right warp and weft yarn, see weaving yarn.
Planning a woven construction? We supply the warp and weft yarn to match.
Tools: Cover factor · reed count · all tools.