When you go into a yarn shop or crafts store, it's easy to be overwhelmed by all the choices. Which yarn is right for your project? Most people stick to the exact type (and even the color!) of yarn suggested in the pattern, but that's not much fun. It's also not necessary as long as you understand something about yarn weights. The Standard Yarn Weight System Yarn weight refers to the thickness of the yarn. It's a range, from super fine to super bulky. There are six different categories of yarn weights, and according to the Craft Yarn Council of America, specific weights of yarn should produce a somewhat predictable number of stitches when using a particular sized needle. The higher the number, the heavier the yarn and the fewer stitches per inch you will get.