Cupful/ˈkʌpfʊl/ Definition 1 of 1Pro Tip 1/3Measurement Unit A 'cupful' refers to a fixed unit of measure in recipes, equivalent to 8 fluid ounces in the US. The recipe calls for one cupful of milk. Pro Tip 2/3Exactness Varies 'Cupful' can imply precision in baking but can be approximate in everyday language. I just need a cupful of rice for dinner. Pro Tip 3/3Non-Liquid Use Although 'cupful' often relates to liquids, it's also used for solids like flour or sugar. Add a cupful of chopped nuts to the cookie dough.