I measured out a cup but counted it as 2 servings because I have no idea how to figure out what 2 oz of dry pasta to cooked is, and thought 2 would be safe. If anyone knows, that would really help in the future, thanks!
I think one cup is a serving, but I don't have a food scale so I can't say for certain.
What I do when cooking spaghetti is look at the box to see how many servings the whole box makes, usually 8. Then, by dividing that up, I can tell how much one serving would be. For example, I usually only make 1/2 a box at a time, or 4 servings. It is easy to separate the cooked pasta in half, then half again to get 4 equal portions, 2oz each. In my experience, each serving of cooked spaghetti comes to about a cup.
Spaghetti uses comes to one cup cooked - now, not one tightly pressed down, fills every empty air gap cup like I try to measure... Other pastas are different. I usually weigh all the cooked pasta and divide by number of servings in the box.