How much is 3 a third of a cup raw oatmeal?

Three is not a third of a cup; rather, it is a whole number. If you mean to ask how much a third of a cup of raw oatmeal is, it would be approximately 1.33 ounces or about 38 grams. If you meant to ask how much three cups of raw oatmeal would be, that would equal 24 ounces or about 680 grams.