Pattern Stiches vs Yarn Stiches

If a pattern says 20 sts & 28 rows = 4 inches w/ size 7 needles and all the yarn is sized up in size 8 needles. How do I find out what yarn would fit my pattern?

Rosinha

You want to knit to the gauge in the pattern which seems to be worsted weight, which is also yarn that can be knit on size 8s. You have to see if you can get 20 sts/4" on size 7s - you may need to use size 8s or 6s depending on if you knit tight or loose.