That's a very useful chart. But it's only a guideline. Remember: the right needle is the one that gives you the gauge you need. Depending on how tightly or loosely you knit, it may be several sizes different from the average. I usually have to go down at least two needle sizes from the recommended. Usually. Occasionally, with smaller sizes, I knit tighter, and have to go up a size. The only way to be sure you've got the right needle size is to swatch.