So, generally speaking, 8 oz of pasta is equal to about 2 cups of cooked pasta. But, here's the thing: it really depends on the type of pasta you're using! Some shapes are more dense than others, which can affect the overall quantity.
For example, if you're using long, thin pasta like spaghetti or angel hair, 8 oz will yield about 2.5 cups of cooked goodness. But, if you're using short, stout pasta like penne or rigatoni, you're looking at more like 2 cups. Make sense?