1 3 cup to oz As we know there are 8 fluid ounces in a cup of US standard. So, by keeping in mind total no. of fluid ounces in a cup, we determine that How many ounces in 1/3 of a cup?. The answer is 2.67 U.S fluid ounces in 1/3 of a cup. We came to know by dividing the cups with the number of fluid ounces in a cup. more