This is important because a standard cup, the one we use to pour on the coffee or tea is six ounces while the cup that is used as a standard of measurement has no universal conversion to ounces. Now, why is there a need to measure cups to ounces and vice versa? According to Cooking Light, the main reason behind this is cooking.

See this conversion table below for precise 1/3 cup to oz conversion. Convert 1/3 cup to oz Note To Measuring 1/3 cup in ounces Measuring dry ingredients (such as flour, butter, cocoa powder etc.) by weight (oz instead of cups) will provide much more accurate results in cooking.