If you can't find a chart, you can always knit up a 5inch swatch in whatever yarn you want to use, and see how it compares to what the pattern directions say. Then you can make adjustments (bigger or smaller needles) if you need to, make a new swatch and then compare again. The new Stitch and Bitch Nation book has a huge section on making changes to existing patterns, from changing yarn and needles to adjusting the pattern for alargers/smaller size to designing your own patterns. I liked the patterns in the book, so I bought it, but you could always check it out of the library (or borrow from a knitty friend). Here's link to the book on the author's blog : http://www.bust.com/knithappens/snb_nation.shtml
..... And just an FYI to anyone who bought/wants to buy the book (or the first stitch and bitch) make sure you check the wbesite for pattern corrections!!!!