This website shows a chart with the different yarn sizes, also known as weights. There are various names for each size which are listed in the chart. The website also gives the needle or crochet hook size that wi
This website mentions the various sizes of yarn and gives a description of what they might be used for. The website also talks about the various types of yarn and gives a description.
Founded in 2007, Ravelry is a free community site, organizational tool, and a yarn/pattern database for knitters and crocheters. In order to use the site, you must create your own (free) account.