Sorry, hit submit too soon!!
With salad it is easy, you can see how it fills the plate, but if I am making (for example) spag bol - my veg looks nearer half when it is raw but when cooked doesn't look as much (IYKWIM) Also, I made roasted veg the other day - when I chopped it all up it looked like masses, faar too much for two people, yet when it was cooked it was fine.
So at what point of the cooking process do you decide it is a third?