Evenness (or uniformity) of yarn|U%| CVm%

What Are CVm% and U%?

 
Both CVm% and U% measure the evenness (or uniformity) of yarn — in simple terms, how consistent the yarn thickness is along its length.

U%  

U% measures the average deviation from the mean thickness (mass or diameter) of yarn.
 

U% = (Average Deviation / Mean Value) × 100

If the yarn mass varies 1.5 tex above/below the average of 30 tex: U% = (1.5 / 30) × 100 = 

5.0% Lower U% = More even yarn = Better quality

U% is simple but less sensitive than CVm%.

CVm% (Coefficient of Variation of Mass Percent): CVm% measures the standard deviation of yarn mass variation,
expressed as a percentage of the mean. It gives a more statistically accurate and sensitive measurement than U%
because it considers all deviations (small and large)
CVm% = (Standard Deviation / Mean) × 100