Altering the gauge

I have a pattern for a children’s lightweigth jacket that is knit in Berroco Sox yarn, gauge 30 stitches = 4", on #2 needle. Figuring that might take forever, I was wondering if I can change the gauge to a sport yarn or DK weight, and therefore use a larger needle? A sport yarn weight would be about 22 stitches = 4" on #6. Would it be a simple matter of figuring our the math? How would you figure yardage?

Yes, figure out what gauge [B]you[/B] get with the yarn and needles, not what’s on the label. Then either knit a smaller size or convert the original pattern stitches to inches, then from inches into your stitch gauge. Adjust for length. As for yardage, it may be about the same length or maybe less.