Abbreviations and Symbols - Yarn Weights
Yarns are available in a variety of weights. Weight refers to the thickness of the strand and fiber contents. Yarn is available in either a long center-pull skein or a ball (some hand-dyed and specialty yarns may be available in unwound hanks which will need to be wound into balls before using). The weight of the skeins or ball and the total yardage is determined by the weight of the strand of yarn.
There are seven standard yarn weight groups determined by members of the Craft Yarn Council of America (CYCA), and the weights are noted with a number and symbol. Many manufacturers use these weights as a guide to consumers who may wish to substitute one yarn for the yarn specified in their pattern instructions.
The CYCA yarn chart was recently updated to add a weight category for the extra-fine yarns used for knitting lace and some sock patterns. Size 10 crochet cotton is also included in this category.