Thread Count & Cover Factor Calculator
Combine ends and picks per inch into a thread count and warp:weft balance, and — when you know the yarn counts — the Peirce cover factor that tells you how tightly the cloth is actually woven.
Thread count & cover
Add both warp and weft yarn counts (Ne) to see Peirce cover factors.
Beyond the marketing number
Thread count is a useful shorthand, but it only counts threads — it says nothing about how thick they are or how much of the surface they cover. Two fabrics with the same count can feel completely different. The warp:weft balance hints at the construction (a plain balanced weave versus a warp-faced twill), while the cover factor puts a real number on tightness by weighing thread spacing against yarn fineness.
That is why premium sheeting is better judged by fibre, yarn count, and cover than by a headline thread count alone. Count each plied yarn once and enter its resultant count (2/80s is 40), and a cloth labelled 600 that is really 300 of 2-ply yarn reads as what it is.
Frequently Asked Questions
How is thread count calculated?
Thread count is the number of threads in one square inch of woven fabric: the ends per inch (EPI, the lengthwise warp) plus the picks per inch (PPI, the crosswise weft). A sheet with 100 EPI and 80 PPI has a thread count of 180.
What are ends and picks?
Ends are the warp yarns that run the length of the fabric on the loom; picks are the weft yarns that cross them. Counting how many of each fall in an inch — often with a linen tester or pick glass — gives EPI and PPI, the two numbers behind thread count.
Is a higher thread count always better?
Not necessarily. ASTM D3775, the test method for warp end and filling pick count, says to "Count individual warp yarns (ends) and filling yarns (picks) as single units regardless of whether they are comprised of single or plied components." In a 2005 staff opinion letter the US Federal Trade Commission said consumers "could be deceived or misled by the practice of stating an inflated thread count, achieved by multiplying the actual count by the number of plies within the yarn," and gave "300 thread count, 2 ply yarn" as a possible non-deceptive label. Fibre quality, yarn fineness, and finish affect the hand of a fabric at least as much as the raw count.
What is cover factor?
Cover factor describes how much of a fabric's area is covered by yarn — in effect, how tightly it is woven. In Peirce's cotton system the warp cover is EPI ÷ √(warp Ne) and the weft cover is PPI ÷ √(weft Ne). The cloth cover factor combines them as K1 + K2 − (K1·K2)/28. A cover of 28 is full cover: yarns of that count lying side by side with no gap, so the cloth figure tops out at 28.
Why do I need yarn counts for cover factor?
Thread count alone can't tell you how tight a fabric is, because the same number of thick or thin yarns cover very different amounts of area. Cover factor brings in the yarn count (Ne) so that thread spacing is judged against yarn thickness — which is why the tool asks for warp and weft counts to compute it.
Educational reference only. Cover factor uses the Peirce cotton-system approximation; woven-fabric tightness also depends on weave, crimp, and finish.