Rice typically doubles in weight after cooking, and oats increase by about half their dry weight.. weigh them both dry.
If it says 1/4 cup of rice = 150 cal, then 1/2 cup of cooked rice = 150 cal
Likewise, if it says 1/2 cup of oats = 150 calories, then 3/4 of cooked oats would also = 150 calories
This is of course, if they come out a perfect double, or a perfect half in increased weight.
The method 3J explained is incredibly precise and will definitely ensure you're getting what you want to be getting every time.