Yarn groups 0 – 7 are divided by thickness based on Craft Yarn Council’s groups and SuperWash and organic yarn, in addition yarn without yarn group, e.g. effect yarn or yarn for which I have no useful data.
If you are looking for a yarn substitute for a knitting or crochet pattern, try it here. In the Yarn menu you can find different groups of yarns. Sorted by different definitions.
New ones are constantly being added, and right now we have more than 1600 yarns