Yarn weight refers to the thickness of yarn used by knitters, weavers, crocheters and other fiber artists. Changing yarn weight or needle size can have a significant impact on the finished project, so standardized systems have been spread about, as well as conversion systems for regional standards (especially needle sizes).Yarn weight is important in achieving the correct gauge or tension for a particular project and can help with yarn substitution. The Craft Yarn Council of America has developed a system that seeks to standardize the labeled weights of yarn. Most yarns state their weight on the ball band. Some brands use a standardized numbering system that uses 7 ranges of relative thickness of yarn.

The advantages to bulky weight yarn are that it works up quickly, is easy to knit with, and makes for very warm, thick, cozy projects (think deep winter scarves and cowls!).  The disadvantages are that the stitches are not as defined and detailed as when you’re using thinner yarn, it uses up yarn very quickly (since each stitch is larger), and can make projects heavier than you might want them to be, if you’re using it in a pattern that doesn’t call for bulky weight yarn (think: delicate cardigan).