Two yarns of the same count can behave very differently on the machine and in the fabric. Often the reason is evenness — measured as CV%. Here is what it means and why buyers should ask about it.
What CV% measures
CV% (coefficient of variation of mass) describes how much a yarn’s thickness varies along its length. A lower CV% means a more uniform yarn; a higher CV% means more thick-and-thin places. Evenness affects strength, appearance, dye uptake and how cleanly the yarn runs.
Why it matters
- Fabric appearance: uneven yarn shows as streaks, barre and cloudiness.
- Processing: irregular yarn causes more breaks in knitting and weaving.
- Dyeing: uneven mass can dye unevenly.
Related quality parameters
Evenness usually comes alongside imperfections (thin places, thick places and neps, often quoted as IPI) and strength. For single-yarn strength, see our guide on CSP and the CSP calculator. Combed and compact yarns generally post better evenness than carded.
What to ask for
When quality matters, ask your supplier for CV%, IPI and strength figures alongside the count. Consistent values batch to batch are the real signal of a controlled spinning process.
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More in our yarn guides and buyer tools.