Gauge and Changes

[DragonsChest]

I have a pattern that requires 18 stitches and 24 rows = 4" in St st on US 8 needles. The yarn says 5 1/2 sts/inches on size US 6 needles. How do I reconcile this?

And when I do find the proper needle size, will that change the pattern's instructions on how many stitches to cast on and the rest...? If it will - how do I figure that out?

Please help! I'm going to buy some pretty pricy yarn (for me), and I want to get it right. Thanks so much!!!!

[knitqueen]

The goal is to get the same gauge that the pattern asks for, with the yarn that you choose. Therefore you want to choose something with similar recommendations so that getting that gauge won't be a major pain. The only way to know is to buy a ball of the yarn and make a gauge swatch or two. You might find that the particular yarn with the right needle size to get the pattern's gauge forms a fabric that is not to your liking. Too loose, too tight, whatever. You can't know for sure until you've used the yarn.